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Sample records for crystals dispersion relations

  1. Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang Xuefeng [School of Mathematical Sciences, Dalian University of Technology, Dalian 116024 (China); Wang Zhengxiong [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

    2012-07-15

    Three-dimensional plasma crystals under microgravity condition are investigated by taking into account an external magnetic field. The wave dispersion relations of dust lattice modes in the body centered cubic (bcc) and the face centered cubic (fcc) plasma crystals are obtained explicitly when the magnetic field is perpendicular to the wave motion. The wave dispersion relations of dust lattice modes in the bcc and fcc plasma crystals are calculated numerically when the magnetic field is in an arbitrary direction. The numerical results show that one longitudinal mode and two transverse modes are coupled due to the Lorentz force in the magnetic field. Moreover, three wave modes, i.e., the high frequency phonon mode, the low frequency phonon mode, and the optical mode, are obtained. The optical mode and at least one phonon mode are hybrid modes. When the magnetic field is neither parallel nor perpendicular to the primitive wave motion, all the three wave modes are hybrid modes and do not have any intersection points. It is also found that with increasing the magnetic field strength, the frequency of the optical mode increases and has a cutoff at the cyclotron frequency of the dust particles in the limit of long wavelength, and the mode mixings for both the optical mode and the high frequency phonon mode increase. The acoustic velocity of the low frequency phonon mode is zero. In addition, the acoustic velocity of the high frequency phonon mode depends on the angle of the magnetic field and the wave motion but does not depend on the magnetic field strength.

  2. Dispersion relations of elastic waves in one-dimensional piezoelectric/piezomagnetic phononic crystal with initial stresses.

    Science.gov (United States)

    Guo, Xiao; Wei, Peijun

    2016-03-01

    The dispersion relations of elastic waves in a one-dimensional phononic crystal formed by periodically repeating of a pre-stressed piezoelectric slab and a pre-stressed piezomagnetic slab are studied in this paper. The influences of initial stress on the dispersive relation are considered based on the incremental stress theory. First, the incremental stress theory of elastic solid is extended to the magneto-electro-elasto solid. The governing equations, constitutive equations, and boundary conditions of the incremental stresses in a magneto-electro-elasto solid are derived with consideration of the existence of initial stresses. Then, the transfer matrices of a pre-stressed piezoelectric slab and a pre-stressed piezomagnetic slab are formulated, respectively. The total transfer matrix of a single cell in the phononic crystal is obtained by the multiplication of two transfer matrixes related with two adjacent slabs. Furthermore, the Bloch theorem is used to obtain the dispersive equations of in-plane and anti-plane Bloch waves. The dispersive equations are solved numerically and the numerical results are shown graphically. The oblique propagation and the normal propagation situations are both considered. In the case of normal propagation of elastic waves, the analytical expressions of the dispersion equation are derived and compared with other literatures. The influences of initial stresses, including the normal initial stresses and shear initial stresses, on the dispersive relations are both discussed based on the numerical results. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Dispersion properties of photonic crystal fibres

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Broeng, Jes; Dridi, Kim

    1998-01-01

    Approximate dispersion and bending properties of all-silica two-dimensional photonic crystal fibres are characterised by the combination of an effective-index model and classical analysis tools for optical fibres. We believe for the first time to have predicted the dispersion properties of photonic...... crystal fibres. The results strongly indicate that these fibres have potential applications as dispersion managing components...

  4. Dispersion analysis of arbitrarily cut orthorhombic crystals.

    Science.gov (United States)

    Höfer, Sonja; Ivanovski, Vladimir; Uecker, Reinhard; Kwasniewski, Albert; Popp, Jürgen; Mayerhöfer, Thomas G

    2017-06-05

    We developed a measurement and evaluation scheme to perform dispersion analysis on arbitrarily cut orthorhombic crystals based on the schemes developed for triclinic and uniaxial crystals. As byproduct of dispersion analysis the orientations of the crystal axes are found. In contrast to the spectra of arbitrarily cut uniaxial crystals, where the fit routine has to separate two independent principal spectra, the spectra of arbitrarily cut orthorhombic crystals are a combination of three independent spectra and the evaluation scheme gets more complex. Dispersion analysis is exemplary performed on two different crystals, which show different spectral features and different levels of difficulties to evaluate. Neodymium gallate (NdGaO 3 ) has broad overlapping reflections bands while topaz (Al 2 SiO 4 [F, OH] 2 ) has a quite high total number of infrared active bands. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Design and construction of a triple-axis crystal neutron spectrometer and performance testing by means of measurements of dispersion relations in copper

    International Nuclear Information System (INIS)

    Fuhrmann, C.

    1979-01-01

    The Triple-Axis Crystal Neutron Spectrometer is the best instrument for the study of lattice dynamics, when the neutron inelastic scattering technique is used. Design, construction and operation of a triple-axis crystal neutron spectrometer, whose construction was recently finished at IEA are described. The design principles employed are directed to mechanical simplicity, facility of construction and flexibility in operation, with no adapted components to industrial applications were used in the construction. The operational characteristics of the spectrometer, such as the neutron wavelenght of the incoming beam and the resolution have been determined. With the purpose to check the performance of IEA Triple-Axis Crystal Neutron Spectrometer, dispersion relation curves for copper, at room temperature, have been measured. The frequency of phonons propagating along three major symmetry directions have been determined. The measurements were carried out operating the Triple-Axis Spectrometer in the 'sup(→)Q-constant' mode. An excelent agreement could be observed between the results obtained in the present experiment and the data for copper presented in the literature. This comparison indicates that the IEA Triple-Axis Crystal Neutron Spectrometer is in good operational conditions and is able to perform original experiments. Details on the experimental procedures for the case of a Triple-Axis Spectrometer operating in 'sup(→)Q-constant' mode are also presented. (Author) [pt

  6. Performance of a three-axes crystal spectrometer at IEA-Sao Paulo, Brazil: measurements of dispersion relations in copper

    International Nuclear Information System (INIS)

    Fuhrmann, C.; Fulfaro, R.; Vinhas, L.A.

    1978-01-01

    With the purpose to check the performance of IEA Triple Axis Spectrometer of which construction was recently finished, dispersion relation curves for copper at room temperature have been messured. The frequencies of phonons propagating along the three major simmetry directions [xi00] [xixi0] and [xixixi] have been determined. The measurements were carried out operating the Triple Axis Spectrometer in the 'Q constant' mode at neutron energy loss. An excellent agreement could be observed between the results obtained in the present experiment and the accurate data for copper presented in the litterature. In such way, we can conclude that the IEA Triple Axis Spectrometer is in good operational conditions and able to perform original experiments. In this report an outline of the theory of the spectrometer operation and details on the experimental procedures for the case of a Triple Axis Spectrometer operating in the 'Q constant' mode are also presented [pt

  7. A photonic crystal fiber with zero dispersion at 1064 nm

    DEFF Research Database (Denmark)

    Andersen, Peter Andreas

    2002-01-01

    We report on the dispersion properties of a single mode, large core photonic crystal fiber. Using white light interferometry the fiber is found to have zero dispersion at 1064 nm......We report on the dispersion properties of a single mode, large core photonic crystal fiber. Using white light interferometry the fiber is found to have zero dispersion at 1064 nm...

  8. Holographic Polymer-Dispersed Liquid Crystals: Materials, Formation, and Applications

    Directory of Open Access Journals (Sweden)

    Y. J. Liu

    2008-01-01

    Full Text Available By combining polymer-dispersed liquid crystal (PDLC and holography, holographic PDLC (H-PDLC has emerged as a new composite material for switchable or tunable optical devices. Generally, H-PDLC structures are created in a liquid crystal cell filled with polymer-dispersed liquid crystal materials by recording the interference pattern generated by two or more coherent laser beams which is a fast and single-step fabrication. With a relatively ideal phase separation between liquid crystals and polymers, periodic refractive index profile is formed in the cell and thus light can be diffracted. Under a suitable electric field, the light diffraction behavior disappears due to the index matching between liquid crystals and polymers. H-PDLCs show a fast switching time due to the small size of the liquid crystal droplets. So far, H-PDLCs have been applied in many promising applications in photonics, such as flat panel displays, switchable gratings, switchable lasers, switchable microlenses, and switchable photonic crystals. In this paper, we review the current state-of-the-art of H-PDLCs including the materials used to date, the grating formation dynamics and simulations, the optimization of electro-optical properties, the photonic applications, and the issues existed in H-PDLCs.

  9. Geometry of physical dispersion relations

    International Nuclear Information System (INIS)

    Raetzel, Dennis; Rivera, Sergio; Schuller, Frederic P.

    2011-01-01

    To serve as a dispersion relation, a cotangent bundle function must satisfy three simple algebraic properties. These conditions are derived from the inescapable physical requirements that local matter field dynamics must be predictive and allow for an observer-independent notion of positive energy. Possible modifications of the standard relativistic dispersion relation are thereby severely restricted. For instance, the dispersion relations associated with popular deformations of Maxwell theory by Gambini-Pullin or Myers-Pospelov are not admissible. Dispersion relations passing the simple algebraic checks derived here correspond to physically admissible Finslerian refinements of Lorentzian geometry.

  10. Holographic polymer dispersed liquid crystals using vinyltrimethoxysilane

    Science.gov (United States)

    Jeong, Eun Hwa; Kim, Byung Kyu

    2009-04-01

    Various amounts of vinyltrimethoxysilane (VTMOS) have been added to the conventional grating formulation of transmission holographic polymer dispersed liquid crystal (HPDLC) based polyurethane acrylate (PUA). With the addition and increasing amount of VTMOS, contact angle of the film with LC and droplet size of LC monotonically increased, implying that VTMOS segments of the polymers are preferentially exposed to the surfaces and provided greater immiscibility with LC molecules giving rise to an increase in droplet size of LC. However, with VTMOS content over 6 wt%, droplets were coalesced to sizes for random scatterings to lower the off state diffraction efficiency below that of virgin PUA. VTMOS was essential to drive the film by lowering the anchoring strength. The operating voltage monotonically decreased with increasing VTMOS content with a minimum switching voltage of about 15 V with response time of about 8 ms.

  11. Frequency dispersion of flexoelectricity in PMN-PT single crystal

    Science.gov (United States)

    Shu, Longlong; Wan, Meiqian; Jiang, Xiaoning; Li, Fei; Zhou, Naigen; Huang, Wenbin; Wang, Tong

    2017-01-01

    The mechanism of the recent discovered enhanced flexoelectricity in perovskites has brought about numerous controversies which still remain unclear. In this paper, we employed relaxor 0.68Pb(Mg2/3Nb1/3)O3 -0.32PbTiO3 (PMN-PT) single crystals for study. The observed flexoelectric coefficient in PMN-PT single crystal reaches up to 100 μ C /m , and in a relative low frequency range, exhibits an abnormal frequency dispersion phenomenon with a positive relationship with frequency. Such frequency dispersion regulation is different from the normal relaxation behavior that usually occur a time delay, and hence proves the flexoelectricity acting more like bulk effect rather than surface effect in this kind of materials.

  12. Frequency dispersion of flexoelectricity in PMN-PT single crystal

    Directory of Open Access Journals (Sweden)

    Longlong Shu

    2017-01-01

    Full Text Available The mechanism of the recent discovered enhanced flexoelectricity in perovskites has brought about numerous controversies which still remain unclear. In this paper, we employed relaxor 0.68Pb(Mg2/3Nb1/3O3 -0.32PbTiO3 (PMN-PT single crystals for study. The observed flexoelectric coefficient in PMN-PT single crystal reaches up to 100 μC/m, and in a relative low frequency range, exhibits an abnormal frequency dispersion phenomenon with a positive relationship with frequency. Such frequency dispersion regulation is different from the normal relaxation behavior that usually occur a time delay, and hence proves the flexoelectricity acting more like bulk effect rather than surface effect in this kind of materials.

  13. A novel structure of photonic crystal fibre for dispersion ...

    Indian Academy of Sciences (India)

    Madhavi Waghmare

    2017-10-23

    Oct 23, 2017 ... refractive index and geometric parameter of PCF. Keywords. Dispersion compensation; photonic crystal fibre; refractive index. 1. Introduction. The development of transmission rate experiences restric- tions due to dispersion in optic fibre communication field. The best method for reduced dispersion in ...

  14. Chromatic dispersion of liquid crystal infiltrated capillary tubes and photonic crystal fibers

    DEFF Research Database (Denmark)

    Rasmussen, Per Dalgaard; Lægsgaard, Jesper; Bang, Ole

    2006-01-01

    We consider chromatic dispersion of capillary tubes and photonic crystal fibers infiltrated with liquid crystals. A perturbative scheme for inclusion of material dispersion of both liquid crystal and the surrounding waveguide material is derived. The method is used to calculate the chromatic...

  15. Chromatic Dispersion Compensation Using Photonic Crystal Fibers with Hexagonal Distribution

    Directory of Open Access Journals (Sweden)

    Erick E. Reyes-Vera

    2013-11-01

    Full Text Available In this paper we show various configurations of photonic crystal fiber with hexagonal holes distribution for compensation of chromatic dispersion in optical communications links. The vectorial finite element method with scattering boundary condition was used for the analysis of the fibers. From these results it was estimated variation of the dispersion and the dispersion slope with respect to change in the diameter of the holes in the microstructure. With the above was possible to obtain values of dispersion in the C and L bands of telecommunications close to -850 ps / nm * km, with confinement losses 10-3 dB / km

  16. Dispersion of low frequency vibrations in the deuterated naphthalene crystal

    International Nuclear Information System (INIS)

    Bokhenkov, E.L.; Sheka, E.; Natkaniec, I.

    1977-01-01

    The dispersion curves of the lattice vibrations and of the two lowest intramolecular vibrations in d 8 -naphthalene (C 10 D 8 ) crystal have been measured by coherent inelastic neutron scattering for the [010] and the [100] directions at the temperature of 98 K and partially at 5 K. The results are compared with calculations based on the Kitaigorodskii parameters for C-C, C-H and H-H interactions in organic molecular crystals. (author)

  17. Positron-atom dispersion relations

    International Nuclear Information System (INIS)

    Dumbrajs, O.; Martinis, M.

    1983-01-01

    The singularity structure of the forward positron-atom scattering amplitude is studied within the framework of perturbation theory with the use of the Landau rules. The unphysical and anomalous regions in the positron-atom forward dispersion relations are discussed. It is shown that the unphysical region starts at E 0 = -Vertical BarE(Ps)Vertical Bar+Vertical BarE 1 Vertical Bar and the anomalous region at E/sub a/ = -(√2Vertical BarE(Ps)Vertical Bar - √Vertical BarE 1 Vertical Bar ) 2 , where E(Ps) and E 1 are correspondingly the positronium and the atomic-electron binding energies. The anomalous region is on the physical sheet if Vertical BarE(Ps)Vertical Bar/2>Vertical BarE 1 Vertical Bar

  18. Axial dispersion in a Kureha Crystal Purifier (KCP)

    Science.gov (United States)

    Otawara, K.; Matsuoka, T.

    2002-04-01

    It is widely accepted that the degree of axial back-mixing in the equipment affects the performance of a column crystallizer. Specifically, small such mixing is inevitable for obtaining highly pure crystal. In fact, it is believed that scale-up of some column crystallizers has been terminated due to the large axial back-mixing or maldistribution. Thus, experiments have been performed for estimating axial dispersion coefficients of liquid phase representing axial back-mixing in the column of a Kureha Crystal Purifier (KCP). The effect of the column diameter on such coefficients has been investigated and it has become evident that the axial back-mixing in the column is more significant in the larger column. Nevertheless, the results have also indicated that the axial back-mixing in KCPs of industrial sizes can be substantially smaller than those in other types of column crystallizers.

  19. Tailoring Dispersion properties of photonic crystal waveguides by topology optimization

    DEFF Research Database (Denmark)

    Stainko, Roman; Sigmund, Ole

    2007-01-01

    The paper describes a systematic method for the tailoring of dispersion properties of slab-based photonic crystal waveguides. The method is based on the topology optimization method which consists in repeated finite element frequency domain analyzes, analytical sensitivity analyzes and gradient...... curve and design of a wide bandwidth, constant low group velocity waveguide demonstrate the efficiency of the method....

  20. Dispersive crystal field excitations and quadrupolar interactions in UPd3.

    Science.gov (United States)

    Le, M D; McEwen, K A; Rotter, M; Jensen, J; Bewley, R I; Guidi, T; Fort, D

    2012-01-25

    We report inelastic neutron scattering measurements and random phase approximation calculations of the dispersive crystal field excitations of UPd(3). The measured spectra at lower energies agree with those calculated using quadrupolar interaction parameters deduced from bulk and x-ray scattering measurements. The more intense excitations arising from the hexagonal sites were used to obtain exchange parameters which proved to be anisotropic.

  1. Dispersive crystal field excitations and quadrupolar interactions in UPd3

    OpenAIRE

    Le, M.D.; McEwen, K.A.; Rotter, M.; Jensen, J.; Bewley, R.I.; Guidi, T.; Fort, D

    2012-01-01

    We report inelastic neutron scattering measurements and random phase approximation calculations of the dispersive crystal field excitations of UPd3. The measured spectra at lower energies agree with those calculated using quadrupolar interaction parameters deduced from bulk and x ray scattering measurements. The more intense excitations arising from the hexagonal sites were used to obtain exchange parameters which proved to be anisotropic

  2. Dispersive photonic crystals from the plane wave method

    Energy Technology Data Exchange (ETDEWEB)

    Guevara-Cabrera, E.; Palomino-Ovando, M.A. [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Apdo. Post. 165, Puebla, Pue. 72000, México (Mexico); Flores-Desirena, B., E-mail: bflores@fcfm.buap.mx [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Apdo. Post. 165, Puebla, Pue. 72000, México (Mexico); Gaspar-Armenta, J.A. [Departamento de Investigación en Física de la Universidad de Sonora Apdo, Post 5-088, Hermosillo Sonora 83190, México (Mexico)

    2016-03-01

    Nowadays photonic crystals are widely used in many different applications. One of the most used methods to compute their band structure is the plane wave method (PWM). However, it can only be applied directly to non-dispersive media and be extended to systems with a few model dielectric functions. We explore an extension of the PWM to photonic crystals containing dispersive materials, that solves an eigenvalue equation for the Bloch wave vectors. First we compare our calculation with analytical results for one dimensional photonic crystals containing Si using experimental values of its optical parameters, and obtainig very well agreement, even for the spectrum region with strong absorption. Then, using the same method, we computed the band structure for a two dimensional photonic crystal without absorption, formed by an square array of MgO cylinders in air. The optical parameters for MgO were modeled with the Lorentz dielectric function. Finally, we studied an array of MgO cylinders in a metal, using Drude model without absorption, for the metal dielectric function. For this last case, we study the gap–midgap ratio as a function of the filling fraction for both the square and triangular lattice. The gap–midgap ratio is larger for the triangular lattice, with a maximum value of 10% for a filling fraction of 0.6. Our results show that the method can be applied to dispersive materials, and then to a wide range of applications where photonic crystals can be used.

  3. Dichroic dye-dependent studies in guest-host polymer-dispersed liquid crystal films

    Energy Technology Data Exchange (ETDEWEB)

    Malik, Praveen, E-mail: pmalik100@yahoo.co [Department of Physics, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar 144011, Punjab (India); Raina, K.K. [Liquid Crystal Group, Materials Research Laboratory, School of Physics and Materials Science, Thapar University, Patiala 147004, Punjab (India)

    2010-01-01

    Guest-host polymer-dispersed liquid crystal (GHPDLC) films were prepared using a nematic liquid crystal, photo-curable polymer and dichroic dye (anthraquinone blue) by polymerization-induced phase separation (PIPS) technique. Non-ionic dichroic dye (1%, 2% and 4% wt./wt. ratio) was taken as guest in PDLC host. Polarizing microscopy shows that in the absence of electric field, liquid crystal (LC) droplets in polymer matrix mainly exhibit bipolar configuration, however, relatively at higher field, maltese-type crosses were observed. Our results show that approx1% dye-doped PDLC film shows better transmission and faster response times over pure polymer-dispersed nematic liquid crystal (PDNLC) and higher concentrated (2% and 4%) GHPDLC films.

  4. Dynamical properties of aluminium from experimental dispersion relations

    International Nuclear Information System (INIS)

    Salles Filho, J.B.V.; Fulfaro, R.; Vinhas, L.A.

    1987-05-01

    Measurements of phonon dispersion relations of aluminium along the high symmetry directions were performed by coherent inelastic scattering of thermal neutrons technique. All measurements were taken at room temperature using the IPEN triple axis neutorn spectrometer. The results obtained with accuracy are in good agreement with the published data. The dispersion relations were calculated theoretically within the framework of Born-von Karman and Axially Symmetric models, including interactions up to the fifth nearest shell of atoms. The elastic constants were determined using the values of sound propagating velocity obtained directly from the dispersion relations along of high symmetry directions of the crystal. Applying theoretical models the force constants of aluminium were also determined. From these data several physical properties of the metal can be obtained. (Author) [pt

  5. Dispersion relation and relative intensity for double-plasmon satellites

    International Nuclear Information System (INIS)

    Srivastava, K.S.; Shiv Singh; Harsh, O.K.

    1981-01-01

    An expression for the dispersion relation and the relative intensity of double-plasmon oscillations and satellites has been derived by extending the dispersion relation and the extended Bohm and Pines Hamiltonian to second order. The calculated value of the relative intensity of the double-plasmon satellite for Be agrees fairly well with the value observed experimentally by other workers. (orig.)

  6. Phonon dispersion relations for caesium thiocyanate

    International Nuclear Information System (INIS)

    Irving, M.A.; Smith, T.F.; Elcombe, M.M.

    1984-01-01

    Room temperature phonon dispersion relations for frequencies below 2 THz have been measured, along the three orthorhombic axes and selected diagonal directions by neutron inelastic scattering, for caesium thiocyanate. These curves, which represent 13 acoustic modes and 11 optic modes of vibration, do not agree with the dispersion behaviour calculated from the rigid-ion model developed by Ti and Ra to describe their Raman scattering observations

  7. Dispersion-tailored, low-loss photonic crystal fibers for the THz range

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Adam, Aurèle J.L.

    2009-01-01

    We have fabricated a new type of photonic crystal fibers based on a cyclic olefin copolymer, transparent in the THz range. We characterize the propagation loss, dispersion, and spatial beam profile in fibers designed for low and high dispersion.......We have fabricated a new type of photonic crystal fibers based on a cyclic olefin copolymer, transparent in the THz range. We characterize the propagation loss, dispersion, and spatial beam profile in fibers designed for low and high dispersion....

  8. Polymer dispersed liquid crystals. Pt.1 Concept, Preparation and Materials

    International Nuclear Information System (INIS)

    Hakemi, H. A.; Santangelo, M.

    1998-01-01

    It is more than a decade since Polymer Dispersed Liquid Crystal (PDLC) film technology became the subject of a world-wide scientific and industrial research and development for commercial applications as large-area reflective displays and electrooptical windows, for privacy, security and light transmission control. In view of current interest and intensive fundamental and industrial research on PDLC, the authors attempt to provide a review of the state-of-art of this technology, from concept to its industrial production, in a series of articles. In the present introductory part, the authors discuss the basic concept, the principle of operation, the materials and the preparation techniques of a PDLC device by phase separation method [it

  9. Slinky-whistler dispersion relation from ``scaling''

    Science.gov (United States)

    Crawford, Frank S.

    1990-10-01

    Slinkies come in two sizes, ``regular'' and ``junior.'' Using 61% of the total length of the regular slinky, a whistler is obtained that sounds to the ear exactly like that obtained using the total length of the junior. That agrees with the proposed (approximate) dispersion relation ω=ck2r. If n is taken to be unknown in an assumed dispersion relation ω=ck(kr)n, then, by ear, with no equipment, it is found out n=0.83±0.17, in reasonable agreement with the proposed n=1.0.

  10. Proton compton scattering in dispersion relation analysis

    International Nuclear Information System (INIS)

    Dumbrajs, Olgierd.

    1978-01-01

    Inserting a logarithmically rising total photon-proton cross section into dispersion relation we update our theoretical knowledge about the forward real part. Taking into account analytic properties of the amplitude in the cosTHETA-variable we find that at low energies our experimental knowledge about this quantity should be modified. (author)

  11. Dispersion relation analysis of proton Compton scattering

    International Nuclear Information System (INIS)

    Dumbrajs, O.

    1979-01-01

    Inserting a logarithmically rising total photon-proton cross section into the dispersion relation, theoretical knowledge about the forward real part is updated. Taking into account analytic properties of the amplitude in the cos theta variable it is found that at low energies, experimental knowledge about this quantity should be reassessed. (Auth.)

  12. Dispersion relations in heavily-doped nanostructures

    CERN Document Server

    Ghatak, Kamakhya Prasad

    2016-01-01

    This book presents the dispersion relation in heavily doped nano-structures. The materials considered are III-V, II-VI, IV-VI, GaP, Ge, Platinum Antimonide, stressed, GaSb, Te, II-V, HgTe/CdTe superlattices and Bismuth Telluride semiconductors. The dispersion relation is discussed under magnetic quantization and on the basis of carrier energy spectra. The influences of magnetic field, magneto inversion, and magneto nipi structures on nano-structures is analyzed. The band structure of optoelectronic materials changes with photo-excitation in a fundamental way according to newly formulated electron dispersion laws. They control the quantum effect in optoelectronic devices in the presence of light. The measurement of band gaps in optoelectronic materials in the presence of external photo-excitation is displayed. The influences of magnetic quantization, crossed electric and quantizing fields, intense electric fields on the on the dispersion relation in heavily doped semiconductors and super-lattices are also disc...

  13. A new design of photonic crystal fiber with ultra-flattened dispersion to simultaneously minimize the dispersion and confinement loss

    Science.gov (United States)

    Olyaee, Saeed; Taghipour, Fahimeh

    2011-02-01

    Photonic crystal fibers (PCFs) are highly suitable transmission media for wavelength-division-multiplexing (WDM) systems, in which low and ultra-flattened dispersion of PCFs is extremely desirable. It is also required to concurrently achieve both a low confinement loss as well as a large effective area in a wide range of wavelengths. Relatively low dispersion with negligible variation has become feasible in the wavelength range of 1.1 to 1.8μm through the proposed design in this paper. According to a new structure of PCF presented in this study, the dispersion slope is 6.8×10-4ps/km.nm2 and the confinement loss reaches below 10-6 dB/km in this range, while at the same time an effective area of more than 50μm2 has been attained. For the analysis of this PCF, finite-difference time-domain (FDTD) method with the perfectly matched layers (PML) boundary conditions has been used.

  14. Dispersive waves induced by self-defocusing temporal solitons in a beta-barium-borate crystal

    DEFF Research Database (Denmark)

    Zhou, Binbin; Bache, Morten

    2015-01-01

    We experimentally observe dispersive waves in the anomalous dispersion regime of a beta-barium-borate (BBO) crystal, induced by a self-defocusing few-cycle temporal soliton. Together the soliton and dispersive waves form an energetic octave-spanning supercontinuum. The soliton was excited...

  15. Modified dispersion relations, inflation, and scale invariance

    Science.gov (United States)

    Bianco, Stefano; Friedhoff, Victor Nicolai; Wilson-Ewing, Edward

    2018-02-01

    For a certain type of modified dispersion relations, the vacuum quantum state for very short wavelength cosmological perturbations is scale-invariant and it has been suggested that this may be the source of the scale-invariance observed in the temperature anisotropies in the cosmic microwave background. We point out that for this scenario to be possible, it is necessary to redshift these short wavelength modes to cosmological scales in such a way that the scale-invariance is not lost. This requires nontrivial background dynamics before the onset of standard radiation-dominated cosmology; we demonstrate that one possible solution is inflation with a sufficiently large Hubble rate, for this slow roll is not necessary. In addition, we also show that if the slow-roll condition is added to inflation with a large Hubble rate, then for any power law modified dispersion relation quantum vacuum fluctuations become nearly scale-invariant when they exit the Hubble radius.

  16. Modified dispersion relations and black hole physics

    International Nuclear Information System (INIS)

    Ling Yi; Li Xiang; Hu Bo

    2006-01-01

    A modified formulation of the energy-momentum relation is proposed in the context of doubly special relativity. We investigate its impact on black hole physics. It turns out that such a modification will give corrections to both the temperature and the entropy of black holes. In particular, this modified dispersion relation also changes the picture of Hawking radiation greatly when the size of black holes approaches the Planck scale. It can prevent black holes from total evaporation, as a result providing a plausible mechanism to treat the remnant of black holes as a candidate for dark matter

  17. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    International Nuclear Information System (INIS)

    Wahle, Markus; Kitzerow, Heinz-Siegfried

    2015-01-01

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage

  18. Low-loss photonic crystal fibers for data transmission and their dispersion properties

    DEFF Research Database (Denmark)

    Nielsen, Martin Dybendal; Jacobsen, Christian; Mortensen, Niels Asger

    2004-01-01

    We report on a single-mode photonic crystal fiber with attenuation and effective area at 1550 nm of 0.48 dB/km and 130 µm2, respectively. This is, to our knowledge, the lowest loss reported for a PCF not made from VAD prepared silica and at the same time the largest effective area for a low-loss ......-loss (future applications of PCFs for data transmission and show for the first time, both numerically and experimentally, how the group velocity dispersion is related to the mode field diameter....

  19. Cascaded interactions between Raman induced solitons and dispersive waves in photonic crystal fibers at the advanced stage of supercontinuum generation.

    Science.gov (United States)

    Driben, Rodislav; Mitschke, Fedor; Zhavoronkov, Nickolai

    2010-12-06

    The complex mechanism of multiple interactions between solitary and dispersive waves at the advanced stage of supercontinuum generation in photonic crystal fiber is studied in experiment and numerical simulations. Injection of high power negatively chirped pulses near zero dispersion frequency results in an effective soliton fission process with multiple interactions between red shifted Raman solitons and dispersive waves. These interactions may result in relative acceleration of solitons with further collisions between them of quasi-elastic or quasi-plastic kinds. In the spectral domain these processes result in enhancement of certain wavelength regions within the spectrum or development of a new significant band at the long wavelength side of the spectrum.

  20. Tailoring nonlinearity and dispersion of photonic crystal fibers using hybrid cladding

    International Nuclear Information System (INIS)

    Zhao-lun, Liu; Lan-tian, Hou; Wei, Wang

    2009-01-01

    We present a hybrid cladding photonic crystal fiber for shaping high nonlinear and flattened dispersion in a wide range of wavelengths. The new structure adopts hybrid cladding with different pitches, air-holes diameters and air-holes arrayed fashions. The full-vector finite element method with perfectly matched layer is used to investigate the characteristics of the hybrid cladding photonic crystal fiber such as nonlinearity and dispersion properties. The influence of the cladding structure parameters on the nonlinear coefficient and geometric dispersion is analyzed. High nonlinear coefficient and the dispersion properties of fibers are tailored by adjusting the cladding structure parameters. A novel hybrid cladding photonic crystal fiber with high nonlinear coefficient and dispersion flattened which is suited for super continuum generation is designed. (author)

  1. Reduced Crystallization Temperature Methodology for Polymer Selection in Amorphous Solid Dispersions: Stability Perspective.

    Science.gov (United States)

    Bhugra, Chandan; Telang, Chitra; Schwabe, Robert; Zhong, Li

    2016-09-06

    API-polymer interactions, used to select the right polymeric matrix with an aim to stabilize an amorphous dispersion, are routinely studied using spectroscopic and/or calorimetric techniques (i.e., melting point depression). An alternate selection tool has been explored to rank order polymers for formation of stable amorphous dispersions as a pragmatic method for polymer selection. Reduced crystallization temperature of API, a parameter introduced by Zhou et al.,1 was utilized in this study for rank ordering interactions in API-polymeric systems. The trends in reduced crystallization temperature monitored over polymer concentration range of up to 20% polymer loading were utilized to calculate "crystallization parameter" or CP for two model systems (nifedipine and BI ABC). The rank order of CP, i.e., a measure of API-polymer interaction, for nifedipine followed the order PVP > PVP-VA > Soluplus > HPMCAS > PV Ac > PAA. This rank ordering was correlated to published results of molecular interactions and physical stability for nifedipine. A different rank ordering was observed for BI ABC: PAA > PVP > HPMCAS > Soluplus > PVPV-VA > PVAc. Interactions for BI ABC were not as differentiated when compared to nifedipine based on CP trends. BI ABC dispersions at drug loadings between 40 and 60% were physically stable for prolonged periods under ICH conditions as well as accelerated stress. We propose that large CP differences among polymers could be predictive of stability outcomes. Acceptable stability at pharmaceutically relevant drug loadings would suggest that the relative influence of downstream processes, such as polymer solubility in various solvents, process suitability and selection, and more importantly supersaturation potential, should be higher compared to stability considerations while developing compounds like BI ABC.

  2. Comment on "Design of a broadband highly dispersive pure silica photonic crystal fiber"

    DEFF Research Database (Denmark)

    Mortensen, Niels Asger

    2008-01-01

    In a recent paper, Subbaraman et al. [Appl. Opt. 46, 3263–3268 (2007)] reported a theoretical and numerical study of highly dispersive pure silica photonic crystal fiber supporting group-velocity dispersion exceeding −2 × 104 ps=nm=km. This Comment argues that the authors consider only one of two...

  3. Continuous-wave wavelength conversion in a photonic crystal fiber with two zero-dispersion wavelengths

    DEFF Research Database (Denmark)

    Andersen, T.V.; Hilligsøe, Karen Marie; Nielsen, C.K.

    2004-01-01

    We demonstrate continuous-wave wavelength conversion through four-wave mixing in an endlessly single mode photonic crystal fiber. Phasematching is possible at vanishing pump power in the anomalous dispersion regime between the two zero-dispersion wavelengths. By mixing appropriate pump and idler...... line width lasers....

  4. Flat super-continuum generation based on normal dispersion nonlinear photonic crystal fibre

    DEFF Research Database (Denmark)

    Chow, K.K.; Takushima, Y.; Lin, C.

    2006-01-01

    Flat super-continuum generation spanning over the whole telecommunication band using a passively modelocked fibre laser source at 1550 nm together with a dispersion-flattened nonlinear photoinc crystal fibre is demonstrated. Since the pulses propagate in the normal dispersion regime of the fibre...

  5. CLSM as quantitative method to determine the size of drug crystals in a solid dispersion

    NARCIS (Netherlands)

    de Waard, Hans; Hessels, Martin J T; Boon, Maarten; Sjollema, Klaas A; Hinrichs, Wouter L J; Eissens, Anko C; Frijlink, Henderik W

    2011-01-01

    PURPOSE: To test whether confocal laser scanning microscopy (CLSM) can be used as an analytical tool to determine the drug crystal size in a powder mixture or a crystalline solid dispersion. METHODS: Crystals of the autofluorescent drug dipyridamole were incorporated in a matrix of crystalline

  6. Novel High Negative Chromatic Dispersion Photonic Crystal Fiber with Low Confinement Loss

    Directory of Open Access Journals (Sweden)

    OUADAH Mohammed Chamse Eddine

    2016-05-01

    Full Text Available In this paper, we propose a novel dual core concentric photonic crystal fiber with high negative chromatic dispersion and low confinement loss. Finite element method with perfectly matched layers (PMLS is used to investigate the guiding properties. In order to achieve a high negative chromatic dispersion, small air holes are added in the inner core as well as the liquid filling the outer core. The numerical results show a negative dispersion coefficient and confinement loss of -78010ps/nm/km, 0.05dB/km respectively at λ=155μm, which make the proposed design an excellent device in high transmission system for dispersion compensation.

  7. Channeling and related crystal effects

    International Nuclear Information System (INIS)

    Uggerhoj, Erik

    1995-01-01

    Channeling, the interaction of particles with oriented crystals, has been applied in a wide variety of scientific and technological areas. A workshop at Aarhus, Denmark, this summer highlighted progress and future directions. Radiation emission has been explored and linked to coherent bremsstrahlung and other oriented crystal radiations. Dramatic effects have been found for ultra-relativistic electrons with Lorentz factors of 105 6. Single crystals are unique for investigations of quantum electrodynamics in strong external fields because probabilities for processes in axial/ planar fields are determined by the magnitude of these fields in the particle rest frame. Erik Uggerhoj of Aarhus reported on an extensive series of experiments concerning radiation emission, pair production, and shower formation carried out at CERN by the NA43 collaboration. As Vladimir Baier of Novosibirsk and Yuri Kononets of Kurchatov noted, theoretical treatment of these interconnected radiation distributions is challenging and much work needs to be done. In general, the agreement with the CERN experiments is good, but many areas like polarization phenomena and particle production need investigation. Prominent among high energy applications is extraction from accelerators. At the workshop, Alexei Asseev reported on beam extraction using a bent crystal at Serpukhov. Konrad Elsener and Jukka Klem reviewed recent CERN SPS studies driven by the possibility of using crystals for extraction of LHC beams. Thornton Murphy of Fermilab announced a step in that direction, with a demonstration this summer of extraction from the Tevatron at 900 GeV. Bent crystal channeling is also used for handling extracted high energy beams. Niels Doble presented a beautiful example of a beam for the CERN NA48 CP-violation experiment. Yuri Chesnokov reported that beams had been deflected through angles up to 150 milliradians at Serpukhov

  8. Nuclear magnetic resonance study of epoxy- based polymer-dispersed liquid crystal droplets

    CERN Document Server

    Han, J W

    1998-01-01

    In this work, polymer-dispersed liquid crystals (PDLC) samples were prepared and studied by nuclear magnetic resonance. Proton NMR spectra and spin-lattice relaxations of 4-cyano-4'-pentylbiphenyl(5CB) and p-methoxybenzylidene-p-n-butylaniline (MBBA) liquid crystals confined in microdroplets were measured. The experimental results were compared with those of the liquid crystals in the pores of silica-gels and with those of the mixing components. The experimental results indicated that the nematic ordering in the microdroplets differed markedly from that observed in bulk nematic crystals. In addition, we examined spin-lattice relaxation mechanisms. The proton spin-lattice relaxation mechanisms in bulk nematic liquid crystals are well established. However, when nematic liquid crystals are confined in microdroplets, the relaxation mechanisms are expected to be affected. We examined possible relaxation mechanisms to explain the observed increase in the spin-lattice relaxation rate of liquid crystals confined in m...

  9. A novel structure of photonic crystal fibre for dispersion ...

    Indian Academy of Sciences (India)

    The newly designed PCF with defect introduced isrecorded over transmission spectrum range 146.7–256.98 THz, i.e., 1.16–2.04 lm. The modal characteristics and dispersion compensation of 2D PCF with circular air holes defect introduced are investigated and compared to those of conventional hexagonal 2D PCF.

  10. Symmetry Breaking in Photonic Crystals: On-Demand Dispersion from Flatband to Dirac Cones.

    Science.gov (United States)

    Nguyen, H S; Dubois, F; Deschamps, T; Cueff, S; Pardon, A; Leclercq, J-L; Seassal, C; Letartre, X; Viktorovitch, P

    2018-02-09

    We demonstrate that symmetry breaking opens a new degree of freedom to tailor energy-momentum dispersion in photonic crystals. Using a general theoretical framework in two illustrative practical structures, we show that breaking symmetry enables an on-demand tuning of the local density of states of the same photonic band from zero (Dirac cone dispersion) to infinity (flatband dispersion), as well as any constant density over an adjustable spectral range. As a proof of concept, we demonstrate experimentally the transformation of the very same photonic band from a conventional quadratic shape to a Dirac dispersion, a flatband dispersion, and a multivalley one. This transition is achieved by finely tuning the vertical symmetry breaking of the photonic structures. Our results provide an unprecedented degree of freedom for optical dispersion engineering in planar integrated photonic devices.

  11. Symmetry Breaking in Photonic Crystals: On-Demand Dispersion from Flatband to Dirac Cones

    Science.gov (United States)

    Nguyen, H. S.; Dubois, F.; Deschamps, T.; Cueff, S.; Pardon, A.; Leclercq, J.-L.; Seassal, C.; Letartre, X.; Viktorovitch, P.

    2018-02-01

    We demonstrate that symmetry breaking opens a new degree of freedom to tailor energy-momentum dispersion in photonic crystals. Using a general theoretical framework in two illustrative practical structures, we show that breaking symmetry enables an on-demand tuning of the local density of states of the same photonic band from zero (Dirac cone dispersion) to infinity (flatband dispersion), as well as any constant density over an adjustable spectral range. As a proof of concept, we demonstrate experimentally the transformation of the very same photonic band from a conventional quadratic shape to a Dirac dispersion, a flatband dispersion, and a multivalley one. This transition is achieved by finely tuning the vertical symmetry breaking of the photonic structures. Our results provide an unprecedented degree of freedom for optical dispersion engineering in planar integrated photonic devices.

  12. Photonic Crystal Fibres for Dispersion and Sensor Applications

    DEFF Research Database (Denmark)

    Sørensen, Thorkild

    2005-01-01

    of the involved nonlinear processes. A hollow-core photonic crystal fibre (HC-PCF) is used as a sensor for gas. It is filled with two gasses, 12C2H2 acetylene, and H13CN hydrogen cyanide, and the transmission spectra are subject for a discussion. A model for infusion speed of fluids to a capillary presented...

  13. Electromagnetic diode based on photonic crystal cavity with embedded highly dispersive meta-interface

    Science.gov (United States)

    Chen, Yongqiang; Dong, Lijuan; Xu, Xiaohu; Jiang, Jun; Shi, Yunlong

    2017-12-01

    In this paper, we propose a scheme for subwavelength electromagnetic diodes by employing a photonic crystal (PC) cavity with embedded electromagnetically induced-transparency (EIT)-like highly dispersive meta-interface. A nonreciprocal response, with 21.5 dB transmission light contrast and 12.3 dBm working power, is conceptually demonstrated in a microstrip transmission line system with asymmetric absorption and nonlinear medium inclusion. Such high-contrast transmission and relatively low-threshold diode action stem from the composite PC-EIT mechanism. This mechanism not only possesses a large quality factor and strong localization of fields but also does not enlarge the device volume and drastically reduce transmittance. Our findings should be beneficial for the design of new and practical metamaterial-enabled nonlinear devices.

  14. Fabrication of Microcapsules for Dye-Doped Polymer-Dispersed Liquid Crystal-Based Smart Windows.

    Science.gov (United States)

    Kim, Mingyun; Park, Kyun Joo; Seok, Seunghwan; Ok, Jong Min; Jung, Hee-Tae; Choe, Jaehoon; Kim, Do Hyun

    2015-08-19

    A dye-doped polymer-dispersed liquid crystal (PDLC) is an attractive material for application in smart windows. Smart windows using a PDLC can be operated simply and have a high contrast ratio compared to those of other devices that employed photochromic or thermochromic material. However, in conventional dye-doped PDLC methods, dye contamination can cause problems and has a limited degree of commercialization of electric smart windows. Here, we report on an approach to resolve dye-related problems by encapsulating the dye in monodispersed capsules. By encapsulation, a fabricated dye-doped PDLC had a contrast ratio of >120 at 600 nm. This fabrication method of encapsulating the dye in a core-shell structured microcapsule in a dye-doped PDLC device provides a practical platform for dye-doped PDLC-based smart windows.

  15. Infrared dispersion analysis and Raman scattering spectra of taurine single crystals

    Science.gov (United States)

    Moreira, Roberto L.; Lobo, Ricardo P. S. M.; Dias, Anderson

    2018-01-01

    A comprehensive set of optical vibrational modes of monoclinic taurine crystals was determined by Raman scattering, and infrared reflectivity and transmission spectroscopies. By using appropriate scattering/reflection geometries, the vibrational modes were resolved by polarization and the most relevant modes of the crystal could be assigned. In particular, we were able to review the symmetry of the gerade modes and to resolve ambiguities in the literature. Owing to the non-orthogonal character of Bu modes in monoclinic crystals (lying on the optic axial plane), we carried out a generalized Lorentz dispersion analysis consisting of simultaneous adjust of infrared-reflectivity spectra at various light polarization angles. The Au modes (parallel to the C2-axis) were treated within the classical Lorentz model. The behavior of off-diagonal and diagonal terms of the complex dielectric tensors and the presence of anomalous dispersion were discussed as consequences of the low symmetry of the crystal.

  16. Analysis of a broadband dispersion compensating photonic crystal fiber raman amplifier

    DEFF Research Database (Denmark)

    Varshney, Shailendra K.; Saitoh, K.; Koshiba, M.

    2006-01-01

    Using an accurate full-vectorial finite element method, a realistic model of a fabricated dispersion compensating photonic crystal fiber is analyzed. An almost flat Raman-gain spectrum (gain-ripples at just ±0.48-dB) is obtained using a single pump.......Using an accurate full-vectorial finite element method, a realistic model of a fabricated dispersion compensating photonic crystal fiber is analyzed. An almost flat Raman-gain spectrum (gain-ripples at just ±0.48-dB) is obtained using a single pump....

  17. Comparison between different dispersion engineering methods in slow light photonic crystal waveguides

    DEFF Research Database (Denmark)

    Wang, Fengwen; Jensen, Jakob Søndergaard; Sigmund, Ole

    2011-01-01

    This paper compares the performance of different dispersion engineering methods in slow light photonic crystal waveguides, i.e., geometrical parameter optimization and topology optimization. In both methods, the design robustness is enforced by considering the dilated, intermediate and eroded...... that waveguides with optimized hole sizes and positions can be efficient for dispersion engineering but that large improvements are possible if irregular geometries are allowed using topology optimization....

  18. Strength of Drug–Polymer Interactions: Implications for Crystallization in Dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Mistry, Pinal; Suryanarayanan, Raj

    2016-09-07

    We investigated the influence of the strength of drug–polymer interactions on the crystallization behavior of a model drug in amorphous solid dispersions (ASDs). Ketoconazole ASDs were prepared with each poly(acrylic acid), poly(2-hydroxyethyl methacrylate), and polyvinylpyrrolidone. Over a wide temperature range in the supercooled region, the α-relaxation time was obtained, which provided a measure of molecular mobility. Isothermal crystallization studies were performed in the same temperature interval using either a synchrotron (for low levels of crystallinity) or a laboratory X-ray (for crystallization kinetics) source. The stronger the drug–polymer interaction, the longer was the delay in crystallization onset time, indicating an increase in physical stability. Stronger drug–polymer interactions also translated to a decrease in the magnitude of the crystallization rate constant. In amorphous ketoconazole as well as in the dispersions, the coupling coefficient, a measure of the extent of coupling between relaxation and crystallization times was ~0.5. This value was unaffected by the strength of drug–polymer interactions. On the basis of these results, the crystallization times in ASDs were predicted at temperatures very close to Tg, using the coupling coefficient experimentally determined for amorphous ketoconazole. The predicted and experimental crystallization times were in good agreement, indicating the usefulness of the model.

  19. Improvements in or relating to dispersions

    International Nuclear Information System (INIS)

    Woodhead, J.L.

    1981-01-01

    A process is described for the preparation of an aqueous dispersion of ceria which comprises forming a slurry of cerium IV hydroxide with water and an acid, the acid being capable of causing deaggregation of aggregated crystallites in the cerium IV hydroxide, heating the slurry for such a time and at such a temperature that the pH reaches a steady value, the quantity of acid in the slurry being such that the steady value of pH is below 5.4, thereby to produce a conditioned slurry, and admixing water with the conditioned slurry to produce an aqueous dispersion of ceria. (author)

  20. Moving Schwarzschild black hole and modified dispersion relations

    Energy Technology Data Exchange (ETDEWEB)

    Barrera Hinojosa, Cristian, E-mail: cbarrera.hinojosa@gmail.com [Departamento de Física, Universidad de Santiago de Chile, Casilla 307, Santiago (Chile); López-Sarrión, Justo, E-mail: jujlopezsa@unal.edu.co [Departamento de Física, Universidad de Santiago de Chile, Casilla 307, Santiago (Chile); Departamento de Física, Universidad Nacional de Colombia, 111321, Bogotá (Colombia)

    2015-10-07

    We study the thermodynamics of a moving Schwarzschild black hole, identifying the temperature and entropy in a relativistic scenario. Furthermore, we set arguments in a framework relating invariant geometrical quantities under global spacetime transformations and the dispersion relation of the system. We then extended these arguments in order to consider more general dispersion relations, and identify criteria to rule them out.

  1. Dispersion relations for 1D high-gain FELs

    International Nuclear Information System (INIS)

    Webb, S.D.; Litvinenko, V.N.

    2010-01-01

    We present analytical results for the one-dimensional dispersion relation for high-gain FELs. Using kappa-n distributions, we obtain analytical relations between the dispersion relations for various order kappa distributions. Since an exact solution exists for the kappa-1 (Lorentzian) distribution, this provides some insight into the number of modes on the way to the Gaussian distribution.

  2. Factors affecting crystallization, dispersion, and aggregation of calcium oxalate monohydrate in various urinary environments

    Science.gov (United States)

    Christmas, Kimberly Gail

    The mechanisms for the formation of kidney stones are not well understood. One possible mechanism is the formation of aggregates in the nephron tubules of the kidneys. However, altering the urinary environment may be a method to help prevent the recurrence of the formation of kidney stones. The primary inorganic constituent found in kidney stones of North American patients is calcium oxalate monohydrate (COM). In this research, studies on the effect of mixing rate on COM precipitation showed that rapid mixing compared to slow mixing produced smaller particle sizes and a narrower particle size distribution due to the more uniform supersaturation level. The findings are consistent with the general contention that mixing directly influences nucleation rate while mixing rate has relatively little influence over rate of growth in precipitation processes. Screening and central composite experimental designs are used to determine the effect of various factors on the aggregation and dispersion characteristics of previously grown calcium oxalate monohydrate (COM) crystals in artificial urinary environments of controlled variables. The variables examined are pH, calcium, oxalate, pyrophosphate, citrate, and protein concentrations in ultrapure water and artificial urine. Optical density measurements, zeta potential analysis, particle size analyzer, optical microscopy, AFM force measurements, protein adsorption, and ions and small molecule adsorption have been used to assess the state of aggregation and dispersion of the COM crystals and to elucidate the mechanisms involved in such a complex system. The data indicate that our model protein, mucin, acts as a dispersant. This is attributed to steric hindrance resulting from the adsorbed mucoprotein. Oxalate, however, promotes aggregation. Interesting interactions between protein and oxalate along with protein and citrate are observed. Such interactions (synergistic or antagonistic) are found to depend on the concentrations of

  3. Phonon dispersion relation of liquid metals

    Indian Academy of Sciences (India)

    Abstract. The phonon dispersion curves of some liquid metals, viz. Na (Z = 1), Mg. (Z = 2), Al (Z = 3) and Pb (Z = 4), have been computed using our model potential. The charged hard sphere (CHS) reference system is applied to describe the structural information. Our model potential along with CHS reference system is ...

  4. Dispersion relations for the hyperbolic thermal conductivity, thermoelasticity and thermoviscoelasticity

    Science.gov (United States)

    Vitokhin, Evgeniy Yu.; Ivanova, Elena A.

    2017-11-01

    The Maxwell-Cattaneo heat conduction theory, the Lord-Shulman theory of thermoelasticity and a hyperbolic theory of thermoviscoelasticity are studied. The dispersion relations are analyzed in the case when a solution is represented in the form of an exponential function decreasing in time. Simple formulas that quite accurately approximate the dispersion curves are obtained. Based on the results of analysis of the dispersion relations, an experimental method of determination of the heat flux relaxation time is suggested.

  5. Layered van der Waals crystals with hyperbolic light dispersion

    DEFF Research Database (Denmark)

    Gjerding, Morten Niklas; Petersen, R.; Pedersen, T.G.

    2017-01-01

    -infrared to the ultraviolet. Combined with the emerging field of van der Waals heterostructuring, we demonstrate how the hyperbolic properties can be further controlled by stacking different two-dimensional crystals opening new perspectives for atomic-scale design of photonic metamaterials. As an application, we identify...... candidates for Purcell factor control of emission from diamond nitrogen-vacancy centers.Natural hyperbolic materials retain the peculiar optical properties of traditional metamaterials whilst not requiring artificial structuring. Here, the authors perform a theoretical screening of a large class of natural...

  6. Dispersal patterns of red foxes relative to population density

    Science.gov (United States)

    Allen, Stephen H.; Sargeant, Alan B.

    1993-01-01

    Factors affecting red fox (Vulpes vulpes) dispersal patterns are poorly understood but warranted investigation because of the role of dispersal in rebuilding depleted populations and transmission of diseases. We examined dispersal patterns of red foxes in North Dakota based on recoveries of 363 of 854 foxes tagged as pups and relative to fox density. Foxes were recovered up to 8.6 years after tagging; 79% were trapped or shot. Straight-line distances between tagging and recovery locations ranged from 0 to 302 km. Mean recovery distances increased with age and were greater for males than females, but longest individual recovery distances were by females. Dispersal distances were not related to population density for males (P = 0.36) or females (P = 0.96). The proportion of males recovered that dispersed was inversely related to population density (r = -0.94; n = 5; P = 0.02), but not the proportion of females (r = -0.49; n = 5; P = 0.40). Dispersal directions were not uniform for either males (P = 0.003) or females (P = 0.006); littermates tended to disperse in similar directions (P = 0.09). A 4-lane interstate highway altered dispersal directions (P = 0.001). Dispersal is a strong innate behavior of red foxes (especially males) that results in many individuals of both sexes traveling far from natal areas. Because dispersal distance was unaffected by fox density, populations can be rebuilt and diseases transmitted long distances regardless of fox abundance.

  7. Spatial dispersion in two-dimensional plasmonic crystals: Large blueshifts promoted by diffraction anomalies

    DEFF Research Database (Denmark)

    David, Christin; Christensen, Johan; Mortensen, N. Asger

    2016-01-01

    We develop a methodology to incorporate nonlocal optical response of the free electron gas due to quantum-interaction effects in metal components of periodic two-dimensional plasmonic crystals and study the impact of spatial dispersion on promising building blocks for photonic circuits. Within th...

  8. Photonic crystal waveguides with semi-slow light and tailored dispersion properties

    DEFF Research Database (Denmark)

    Frandsen, Lars Hagedorn; Lavrinenko, Andrei; Fage-Pedersen, Jacob

    2006-01-01

    waveguide with either vanishing, positive, or negative group velocity dispersion and semi-slow light. We realize experimentally a silicon-on-insulator photonic crystal waveguide having nearly constant group velocity [similar to]c$-0$//34 in an 11-nm bandwidth below the silica-line. $CPY@2006 Optical Society...

  9. Dispersion relations and sum rules for natural optical activity

    International Nuclear Information System (INIS)

    Thomaz, M.T.; Nussenzveig, H.M.

    1981-06-01

    Dispersion relations and sum rules are derived for the complex rotatory power of an arbitrary linear (nonmagnetic) isotropic medium showing natural optical activity. Both previously known dispersion relations and sum rules as well as new ones are obtained. It is shown that the Rosenfeld-Condon dispersion formula is inconsistent with the expected asymptotic behavior at high frequencies. A new dispersion formula based on quantum eletro-dynamics removes this inconsistency; however, it still requires modification in the low-frequency limit. (Author) [pt

  10. Layered van der Waals crystals with hyperbolic light dispersion

    DEFF Research Database (Denmark)

    Gjerding, Morten Niklas; Petersen, R.; Pedersen, T.G.

    2017-01-01

    candidates for Purcell factor control of emission from diamond nitrogen-vacancy centers.Natural hyperbolic materials retain the peculiar optical properties of traditional metamaterials whilst not requiring artificial structuring. Here, the authors perform a theoretical screening of a large class of natural......Compared to artificially structured hyperbolic metamaterials, whose performance is limited by the finite size of the metallic components, the sparse number of naturally hyperbolic materials recently discovered are promising candidates for the next generation of hyperbolic materials. Using first......-infrared to the ultraviolet. Combined with the emerging field of van der Waals heterostructuring, we demonstrate how the hyperbolic properties can be further controlled by stacking different two-dimensional crystals opening new perspectives for atomic-scale design of photonic metamaterials. As an application, we identify...

  11. Fabrication of robust crystal balls from the electrospray of soft polymer spheres/silica dispersion.

    Science.gov (United States)

    Shen, Zhehong; Zhu, Yue; Wu, Limin; You, Bo; Zi, Jian

    2010-05-04

    This paper presents a novel and facile approach to fabricate robust crystal balls directly through the self-assembly of soft colloidal polymer spheres by the aid of nano silica using an electrospraying technique. In this approach, soft colloidal polymer spheres are synthesized by emulsion polymerization and then blended with colloidal silica to obtain nanocomposite dispersion. When this dispersion is loaded into an injector and forced to flow through the nozzle under direct electric field, the detached droplets are collected by an oil solvent. As water and solvent evaporate, the colloidal polymer spheres and silica beads can directly self-assemble into robust crystal balls. Neither soft matrix nor post-treatment is needed. The obtained crystal balls have not only excellent mechanical properties to withstand external forces such as cutting, puckering, and bending, but also reversible deformation.

  12. Crystal Microbalance Monitors Relative Humidity

    Science.gov (United States)

    Yang, L. C.

    1984-01-01

    Sensor monitors water evaporation in industrial drying processes. Measured adsorption isotherm for instrument essentially linear over entire range of relative humidity. Testing at each temperature setting less than half hour for full relative-humidity range, with estimated frequency response time less than 10 seconds. Used to measure relative humidity of ambient atmosphere near drying paper, food textile fabrics and pulp to optimize water-drying portion of processing cycle.

  13. Shape-dependent dispersion and alignment of nonaggregating plasmonic gold nanoparticles in lyotropic and thermotropic liquid crystals.

    Science.gov (United States)

    Liu, Qingkun; Tang, Jianwei; Zhang, Yuan; Martinez, Angel; Wang, Shaowei; He, Sailing; White, Timothy J; Smalyukh, Ivan I

    2014-05-01

    We use both lyotropic liquid crystals composed of prolate micelles and thermotropic liquid crystals made of rod-like molecules to uniformly disperse and unidirectionally align relatively large gold nanorods and other complex-shaped nanoparticles at high concentrations. We show that some of these ensuing self-assembled orientationally ordered soft matter systems exhibit polarization-dependent plasmonic properties with strongly pronounced molar extinction exceeding that previously achieved in self-assembled composites. The long-range unidirectional alignment of gold nanorods is mediated mainly by anisotropic surface anchoring interactions at the surfaces of gold nanoparticles. Polarization-sensitive absorption, scattering, and extinction are used to characterize orientations of nanorods and other nanoparticles. The experimentally measured unique optical properties of these composites, which stem from the collective plasmonic effect of the gold nanorods with long-range order in a liquid crystal matrix, are reproduced in computer simulations. A simple phenomenological model based on anisotropic surface interaction explains the alignment of gold nanorods dispersed in liquid crystals and the physical underpinnings behind our observations.

  14. Analysis of a realistic and idealized dispersion compensating photonic crystal fiber Raman Amplifier

    DEFF Research Database (Denmark)

    Varshney, S.K.; Saitoh, K.; Koshiba, M.

    2007-01-01

    In the present paper, the highly efficient Raman amplification properties of a realistic and idealized dispersion compensating photonic crystal fiber (DCPCF) are described numerically. We have used an accurate full-vectorial finite element modal solver with hybrid curvilinear edge/nodal elements...... and anisotropic perfectly matched layers for an accurate modal characterization of the realistic as well as idealized DCPCF. A good agreement is observed between numerically evaluated and experimentally [P.J. Roberts, B.J. Mangan, H. Sabert, F. Couny, et al., J. Opt. Fiber Commun. Rep. 2 (2005) 435-461] measured...... dispersion values. A high peak Raman gain efficiency of 10.5 W-¹?km-¹ is obtained at 13.1 THz frequency shift for a 1455 nm depolarized pump. A DCPCF module of 1-km length can compensate for the dispersion accumulated over 70-km of conventional single mode fiber link with a residual dispersion of +/-50 ps...

  15. Energy-dispersive x-Ray Analysis of Phosphorus, Potassium, Magnesium, and Calcium in Globoid Crystals in Protein Bodies from Different Regions of Cucurbita maxima Embryos 1

    Science.gov (United States)

    Lott, John N. A.; Greenwood, John S.; Vollmer, Catherine M.; Buttrose, Mark S.

    1978-01-01

    The seeds of Cucurbita maxima contain protein bodies with electrondense globoid crystals. Because of their density globoid crystals are ideal material for energy-dispersive x-ray (EDX) analysis studies of elemental composition. Fixation trials were carried out to test globoid crystal extraction during glutaraldehyde fixation, water washing, and ethanol dehydration. Glutaraldehyde fixation without subsequent washing or dehydration alone produced no significant changes in elemental composition of cotyledon globoid crystals. If glutaraldehyde fixation was followed by water washes or ethanol dehydration there was some loss of the major globoid crystal elements but the relative percentages of the elements P, K, Ca, and Mg remained relatively unchanged. In this paper results of a study of the P, K, Mg, and Ca content of globoid crystals in different tissues of squash embryos are presented. The globoid crystals in the radicle were found to be the least dense in the embryo. Globoid crystals from all embryo regions contained P, K, and Mg. In the various embryo regions P and Mg maintained relatively constant proportions of the globoid crystal composition while K and Ca varied. Of particular significance is the distribution of Ca which is generally an immobile element. Calcium was found in highest amounts in the globoid crystals of the radicle and stem regions while globoid crystals in much of the cotyledon contained little, if any, Ca. The Ca storage thus seems to be spatially arranged in a manner that would aid early growth of the root-shoot axis. PMID:16660439

  16. Factoring the dispersion relation in the presence of Lorentz violation

    Energy Technology Data Exchange (ETDEWEB)

    Colladay, Don; McDonald, Patrick; Mullins, David, E-mail: colladay@ncf.ed [New College of Florida, Sarasota, FL 34243 (United States)

    2010-07-09

    We produce an explicit formula for the dispersion relation for the Dirac equation in the standard model extension in the presence of Lorentz violation. Our expression is obtained using novel techniques which exploit the algebra of quaternions. The dispersion relation is found to conveniently factor in two special cases that each involve a mutually exclusive set of nonvanishing Lorentz-violating parameters. This suggests that a useful approach to studies of Lorentz-violating models is to split the parameter space into two separate pieces, each of which yields a simple, tractable dispersion relation that can be used for analysis.

  17. Electrically Tunable Binary-Phase Fresnel Lens Based on Polymer Dispersed Liquid Crystal

    Directory of Open Access Journals (Sweden)

    Hui LI

    2017-08-01

    Full Text Available This is a proposal for a Fresnel lens with an electrically tunable binary-phase made of polymer dispersed liquid crystal (PDLC, which has relatively fast response time and low applied voltage. Simple fabrication is the major advantage of the proposed method. In this study, NOA65 and E7 were utilized with weight ratios of 60 wt.%: 40 wt.%. There was also the utilization of a relatively low intensity UV-light, 0.53 mW/cm2. The duration time of exposure was about 30 hours. The performance improvement of the Fresnel lens resulted from the infiltration of large LC droplet into the PDLC film. The phenomenon of black cross strip patterns could be explained with the use of the electro-hydrodynamics theory. The diffraction efficiency of the proposed lens was from 31.1 % to 41 % with the changes of externally applied voltage. This work presents an effective approach to get relatively complete phase separation in PDLC. The proposed method also provides great potential in developing high performance Fresnel lens.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16317

  18. The Optimization of Dispersion Properties of Photonic Crystal Fibers Using a Real-Coded Genetic Algorithm

    International Nuclear Information System (INIS)

    Yin Guo-Bing; Li Shu-Guang; Liu Shuo; Wang Xiao-Yan

    2011-01-01

    A real-coded genetic algorithm (GA) combined with a fully vectorial effective index method (FVEIM) is employed to design structures of photonic crystal fibers (PCFs) with user defined dispersion properties theoretically. The structures of PCFs whose solid cores are doped GeO 2 with zero-dispersions at 0.7–3.9μm are optimized and the flat dispersion ranges through the R+L+C band and the negative dispersion is −1576.26 ps·km −1 ·nm −1 at 1.55 μm. Analyses show that the zero-dispersion wavelength (ZDW) could be one of many ZDWs for the same fiber structure; PCFs could alter the dispersion to be Battened through the R+L+C band with a single air-hole diameter; and negative dispersion requires high air filling rate at 1.55 μm. The method is proved to be elegant for solving this inverse problem. (fundamental areas of phenomenology(including applications))

  19. The Optimization of Dispersion Properties of Photonic Crystal Fibers Using a Real-Coded Genetic Algorithm

    Science.gov (United States)

    Yin, Guo-Bing; Li, Shu-Guang; Liu, Shuo; Wang, Xiao-Yan

    2011-06-01

    A real-coded genetic algorithm (GA) combined with a fully vectorial effective index method (FVEIM) is employed to design structures of photonic crystal fibers (PCFs) with user defined dispersion properties theoretically. The structures of PCFs whose solid cores are doped GeO2 with zero-dispersions at 0.7-3.9μm are optimized and the flat dispersion ranges through the R+L+C band and the negative dispersion is -1576.26 ps·km-1·nm-1 at 1.55 μm. Analyses show that the zero-dispersion wavelength (ZDW) could be one of many ZDWs for the same fiber structure; PCFs could alter the dispersion to be Battened through the R+L+C band with a single air-hole diameter; and negative dispersion requires high air filling rate at 1.55 μm. The method is proved to be elegant for solving this inverse problem.

  20. Refractive index dispersion sensing using an array of photonic crystal resonant reflectors

    DEFF Research Database (Denmark)

    Hermannsson, Pétur Gordon; Vannahme, Christoph; Smith, Cameron

    2015-01-01

    Refractive index sensing plays a key role in various environmental and biological sensing applications. Here, a method is presented for measuring the absolute refractive index dispersion of liquids using an array of photonic crystal resonant reflectors of varying periods. It is shown...... perform measurements at arbitrary number of wavelengths, and requires only a minute sample volume. The ability to sense a material's dispersion profile offers an added dimension of information that may be of benefit to optofluidic lab-on-a-chip applications. © 2015 AIP Publishing LLC....

  1. Structural deformations in liquid crystals with dispersed magnetic nano-colloids

    Directory of Open Access Journals (Sweden)

    S Shoarinejad

    2012-06-01

    Full Text Available  The stable colloidal dispersions of magnetic nano-particles in nematic liquid crystals are called ferronematics. Their behaviour in magnetic fields depends on various parameters such as anchoring energy, magnetic anisotropy, and shape and volume fraction of the particles. In the present paper, the threshold field is obtained for these colloidal nematics. Then, the influence of magnetic anisotropy, cell thickness, magnetic moment, and volume fraction of the particles are discussed . It is found that due to the influence of some effective parameters, the threshold field changes when compared to pure nematic liquid crystals. The obtained results are consistent with the reported experimental results.

  2. Spatial light modulator using polymer-dispersed liquid crystal: Dependence of resolution on reading light intensity

    Science.gov (United States)

    Takizawa, Kuniharu; Kikuchi, Hiroshi; Fujikake, Hideo; Kodama, Kenichi; Kishi, Kiyoshi

    1994-03-01

    A spatial light modulator consisting of a polymer-dispersed liquid crystal (PDLC) film, a dielectric mirror, and a Bi12SiO20 photoconductor is useful for projection-type displays, optical image processing, and optical computing. However, a portion of the reading light scattered by the PDLC film passes through the dielectric mirror and illuminates the photoconductor, thus causing deterioration of display-image quality. This article reports on the results of a detailed study on the influence of reading light on the resolution and amplification factor, which is the ratio of reading light intensity to the maximum intensity of writing light. Angular distributions of light scattered by a PDLC cell were measured and the results were used to calculate the intensity of scattered light absorbed by the photoconductor. We then analyzed the optical input/output characteristics of the spatial light modulator with regard to the optical feedback effect caused by the reading light in order to discover the parameter for evaluating image quality. The relation between amplification and resolution is derived from this parameter. We have also considered a light absorption layer for preventing the deterioration of image quality and obtained the relation between the amplification factor and the transmittance of the light absorption layer for high definition images of high brightness. Finally, these theoretical results were confirmed by an experiment using a spatial light modulator with no dielectric mirror.

  3. Ultrasonic absorption and velocity dispersion of binary mixture liquid crystal MBBA/EBBA

    International Nuclear Information System (INIS)

    Choi, K.

    1979-01-01

    The effect of phase transitions and the partial magnetic alignment for liquid crystal molecules on the ultrasonic absorption and velocity dispersion has been investigated. The binary mixture of Shiff base liquid crystals MBBA/EBBA (55:45 mole %) showed anomalous ultrasonic absorption and velocity dispersion at eutectic (Tsub(m) = -20 0 C) and clearing point (Tsub(c) = 50 0 C) at the frequency range of 5 MHz, 10MHz, 15MHz and 30 MHz. The experimental data were analyzed in terms of relaxation time and Fixman theory. The anisotropy of the propagation velocity due to the magnetic alignment was about 0.9% (the deviation between velocities propagating parallel and perpendicular to the applied field). (author)

  4. Random lasing in dye-doped polymer dispersed liquid crystal film

    Science.gov (United States)

    Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

    2016-09-01

    A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

  5. Dynamic Time Multiplexing Fabrication of Holographic Polymer Dispersed Liquid Crystals for Increased Wavelength Sensitivity

    Science.gov (United States)

    Fontecchio, Adam K. (Inventor); Rai, Kashma (Inventor)

    2017-01-01

    Described herein is a new holographic polymer dispersed liquid crystal (HPDLC) medium with broadband reflective properties, and a new technique for fabrication of broadband HPDLC mediums. The new technique involves dynamic variation of the holography setup during HPDLC formation, enabling the broadening of the HPDLC medium's wavelength response. Dynamic variation of the holography setup may include the rotation and/or translation of one or more motorized stages, allowing for time and spatial, or angular, multiplexing through variation of the incident angles of one or more laser beams on a pre-polymer mixture during manufacture. An HPDLC medium manufactured using these techniques exhibits improved optical response by reflecting a broadband spectrum of wavelengths. A new broadband holographic polymer dispersed liquid crystal thin film polymeric mirror stack with electrically-switchable beam steering capability is disclosed. XXXX Described herein is a new holographic polymer dispersed liquid crystal (HPDLC) medium with broadband reflective properties, and a new technique for fabrication of broadband 10 HPDLC mediums. The new technique involves dynamic variation of the holography setup during HPDLC formation, enabling the broadening of the HPDLC medium's wavelength response. Dynamic variation of the holography setup may include the rotation and/or translation of one or more 15 motorized stages, allowing for time and spatial, or angular, multiplexing through variation of the incident angles of one or more laser beams on a pre-polymer mixture during manufacture. An HPDLC medium manufactured using these techniques exhibits improved optical response by reflecting 20 a broadband spectrum of wavelengths. A new broadband holographic polymer dispersed liquid crystal thin film polymeric mirror stack with electrically switchable beam steering capability is disclosed.

  6. Frequency and Temperature Dependence of Fabrication Parameters in Polymer Dispersed Liquid Crystal Devices

    Science.gov (United States)

    Torres, Juan C.; Vergaz, Ricardo; Barrios, David; Sánchez-Pena, José Manuel; Viñuales, Ana; Grande, Hans Jürgen; Cabañero, Germán

    2014-01-01

    A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including the influence of the temperature on the elements into it. In addition, a relevant effect of temperature on electrical measurements has been observed. PMID:28788632

  7. GROWTH RATE DISPERSION (GRD OF THE (010 FACE OF BORAX CRYSTALS IN FLOWING SOLUTION

    Directory of Open Access Journals (Sweden)

    Suharso Suharso

    2010-06-01

    Full Text Available The growth rates of borax crystals from aqueous solutions in the (010 direction at various flow rates were measured. The observed variations of the growth rate can be represented by a normal distribution.  It was found that there is no correlation between growth rate distribution and solution flow under these experimental conditions.   Keywords: Growth rate dispersion (GRD, borax, flow rate

  8. Frequency and Temperature Dependence of Fabrication Parameters in Polymer Dispersed Liquid Crystal Devices

    Directory of Open Access Journals (Sweden)

    Juan C. Torres

    2014-05-01

    Full Text Available A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including the influence of the temperature on the elements into it. In addition, a relevant effect of temperature on electrical measurements has been observed.

  9. Spatial dispersion of index components required for building invisibility cloak medium from photonic crystals

    Science.gov (United States)

    Jamilan, Saeid; Semouchkin, George; Gandji, Navid P.; Semouchkina, Elena

    2018-04-01

    The opportunities to use dielectric photonic crystals (PhCs) as the media of cylindrical invisibility cloaks, designed using transformation optics (TO) concepts, are investigated. It is shown that TO-based prescriptions for radial index dispersion, responsible for turning waves around hidden objects, can be dropped if the PhC media support self-collimation of waves in bent crystals. Otherwise, to provide prescribed anisotropy of index dispersion, it is possible to employ PhCs with rectangular lattices. It is found, however, that at acceptable cloak thicknesses, modifications of crystal parameters do not allow for achieving the prescribed level of index anisotropy. This problem is solved by finding the reduced spatial dispersion law for the radial index component, which is characterized by decreased against TO-prescriptions values near the target and increased values in outer layers of the cloak. The cloak utilizing reduced prescriptions for indices is shown to perform almost as efficiently as a TO-based cloak, in terms of both wave front restoration behind the target and reducing the total scattering cross-width of the target.

  10. Buffering capability and limitations in low dispersion photonic crystal waveguides with elliptical airholes.

    Science.gov (United States)

    Long, Fang; Tian, Huiping; Ji, Yuefeng

    2010-09-01

    A low dispersion photonic crystal waveguide with triangular lattice elliptical airholes is proposed for compact, high-performance optical buffering applications. In the proposed structure, we obtain a negligible-dispersion bandwidth with constant group velocity ranging from c/41 to c/256, by optimizing the major and minor axes of bulk elliptical holes and adjusting the position and the hole size of the first row adjacent to the defect. In addition, the limitations of buffer performance in a dispersion engineering waveguide are well studied. The maximum buffer capacity and the maximum data rate can reach as high as 262bits and 515 Gbits/s, respectively. The corresponding delay time is about 255.4ps.

  11. Adsorption of polyethylene glycol (PEG) onto cellulose nano-crystals to improve its dispersity.

    Science.gov (United States)

    Cheng, Dong; Wen, Yangbing; Wang, Lijuan; An, Xingye; Zhu, Xuhai; Ni, Yonghao

    2015-06-05

    In this work, the adsorption of polyethylene glycol (PEG) onto cellulose nano-crystals (CNC) was investigated for preparing re-dispersible dried CNC. Results showed that the re-dispersity of CNC in water can be significantly enhanced using a PEG1000 dosage of 5wt% (based on the dry weight of CNC). The elemental analysis confirmed the adsorption of PEG onto the CNC surface. Transmission electron microscopy (TEM) was used to characterize the dry powder and indicated that the irreversible agglomeration of CNC after drying was essentially eliminated based on the PEG adsorption concept. Thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) suggested that CNC crystallinity and thermal stability were not affected by the adsorption of PEG. Thus, the adsorption of PEG has great potential for producing re-dispersible powder CNC. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Refractive index dispersion sensing using an array of photonic crystal resonant reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Hermannsson, Pétur G.; Vannahme, Christoph; Smith, Cameron L. C.; Sørensen, Kristian T.; Kristensen, Anders, E-mail: anders.kristensen@nanotech.dtu.dk [Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads, Building 345E, DK-2800 Kgs. Lyngby (Denmark)

    2015-08-10

    Refractive index sensing plays a key role in various environmental and biological sensing applications. Here, a method is presented for measuring the absolute refractive index dispersion of liquids using an array of photonic crystal resonant reflectors of varying periods. It is shown that by covering the array with a sample liquid and measuring the resonance wavelength associated with transverse electric polarized quasi guided modes as a function of period, the refractive index dispersion of the liquid can be accurately obtained using an analytical expression. This method is compact, can perform measurements at arbitrary number of wavelengths, and requires only a minute sample volume. The ability to sense a material's dispersion profile offers an added dimension of information that may be of benefit to optofluidic lab-on-a-chip applications.

  13. Enhanced diffraction properties of photoinduced gratings in nematic liquid crystals doped with Disperse Red 1.

    Science.gov (United States)

    Li, Hongjing; Wang, Jianhao; Wang, Changshun; Zeng, Pengfei; Pan, Yujia; Yang, Yifei

    2016-01-01

    Diffraction properties of photoinduced gratings recorded by overlapping two coherent beams at 532 nm in nematic liquid crystals doped with Disperse Red 1 were investigated with a probe beam at 632.8 nm. The grating was formed due to the alignment of dye molecules that leaded to the reorientation of the liquid crystal phase. The diffraction efficiency of the photoinduced grating was found to increase rapidly when the sample temperature was close to the clearing point in the nematic phase and a nearly 30-fold enhancement of the first-order diffraction efficiency was obtained. The pretransitional enhancement of the diffraction efficiency was discussed in terms of the reorientation of liquid crystals, optical nonlinearity effects and the onset of critical opalescence near the nematic-isotropic phase transition. Moreover, a peak shift of diffraction efficiency towards the lower temperature was observed with the increase of recording light intensity, which was attributed to laser induced photochemical disordering.

  14. Complete transmission system with a highly non-linear dispersion shifted photonic crystal fibre as the demultiplexer

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Siahlo, Andrei; Andersen, Peter Andreas

    2003-01-01

    A highly nonlinear 50 m long photonic crystal fibre with zero-dispersion wavelength at 1552 nm is investigated as a 40 to 10 Gb/s demultiplexer in a complete transmission system. 160 to 10 Gb/s is feasible.......A highly nonlinear 50 m long photonic crystal fibre with zero-dispersion wavelength at 1552 nm is investigated as a 40 to 10 Gb/s demultiplexer in a complete transmission system. 160 to 10 Gb/s is feasible....

  15. Dispersion relations for η '→ η π π

    Science.gov (United States)

    Isken, Tobias; Kubis, Bastian; Schneider, Sebastian P.; Stoffer, Peter

    2017-07-01

    We present a dispersive analysis of the decay amplitude for η '→ η π π that is based on the fundamental principles of analyticity and unitarity. In this framework, final-state interactions are fully taken into account. Our dispersive representation relies only on input for the {π π } and {π }η scattering phase shifts. Isospin symmetry allows us to describe both the charged and neutral decay channel in terms of the same function. The dispersion relation contains subtraction constants that cannot be fixed by unitarity. We determine these parameters by a fit to Dalitz-plot data from the VES and BES-III experiments. We study the prediction of a low-energy theorem and compare the dispersive fit to variants of chiral perturbation theory.

  16. Planck-scale-modified dispersion relations in FRW spacetime

    Science.gov (United States)

    Rosati, Giacomo; Amelino-Camelia, Giovanni; Marcianò, Antonino; Matassa, Marco

    2015-12-01

    In recent years, Planck-scale modifications of the dispersion relation have been attracting increasing interest also from the viewpoint of possible applications in astrophysics and cosmology, where spacetime curvature cannot be neglected. Nonetheless, the interplay between Planck-scale effects and spacetime curvature is still poorly understood, particularly in cases where curvature is not constant. These challenges have been so far postponed by relying on an ansatz, first introduced by Jacob and Piran. We propose here a general strategy of analysis of the effects of modifications of the dispersion relation in Friedmann-Robertson-Walker spacetimes, applicable both to cases where the relativistic equivalence of frames is spoiled ("preferred-frame scenarios") and to the alternative possibility of "DSR-relativistic theories," theories that are fully relativistic but with relativistic laws deformed so that the modified dispersion relation is observer independent. We show that the Jacob-Piran ansatz implicitly assumes that spacetime translations are not affected by the Planck scale, while under rather general conditions, the same Planck-scale quantum-spacetime structures producing modifications of the dispersion relation also affect translations. Through the explicit analysis of one of the effects produced by modifications of the dispersion relation, an effect amounting to Planck-scale corrections to travel times, we show that our concerns are not merely conceptual but rather can have significant quantitative implications.

  17. From field theory to phenomenology: the history of dispersion relations

    International Nuclear Information System (INIS)

    Pickering, A.

    1989-01-01

    The authors chart the history of quantum field theory (QFT) in the 1950s with reference to the ideas of dispersion relations. QFT failed to explain strong interaction physics and so was discarded. Connections are drawn between a central group of particle theorists working on applying Kramers-Kronig light scattering relations to high energy particle scattering and the way physics developed. The concepts of single and double dispersion relations and Regge poles, when connected with the large quantity of empirical data from the large particle accelerators of the 1950s, could not be embodied within QFT, which then fell into decline. (UK)

  18. Small-angle light scattering symmetry breaking in polymer-dispersed liquid crystal films with inhomogeneous electrically controlled interface anchoring

    Science.gov (United States)

    Loiko, V. A.; Konkolovich, A. V.; Zyryanov, V. Ya.; Miskevich, A. A.

    2017-03-01

    We have described the method of analyzing and reporting on the results of calculation of the small-angle structure of radiation scattered by a polymer-dispersed liquid crystal film with electrically controlled interfacial anchoring. The method is based on the interference approximation of the wave scattering theory and the hard disk model. Scattering from an individual liquid crystal droplet has been described using the anomalous diffraction approximation extended to the case of droplets with uniform and nonuniform interface anchoring at the droplet-polymer boundary. The director field structure in an individual droplet is determined from the solution of the problem of minimizing the volume density of the free energy. The electrooptical effect of symmetry breaking in the angular distribution of scattered radiation has been analyzed. This effect means that the intensities of radiation scattered within angles +θ s and-θ s relative to the direction of illumination in the scattering plane can be different. The effect is of the interference origin and is associated with asymmetry of the phase shift of the wavefront of an incident wave from individual parts of the droplet, which appears due to asymmetry of the director field structure in the droplet, caused by nonuniform anchoring of liquid crystal molecules with the polymer on its surface. This effect is analyzed in the case of normal illumination of the film depending on the interfacial anchoring at the liquid crystal-polymer interface, the orientation of the optical axes of droplets, their concentration, sizes, anisometry, and polydispersity.

  19. Highly birefringent photonic crystal fiber with ultra-flattened negative dispersion over S + C + L + U bands

    DEFF Research Database (Denmark)

    Habib, Selim; Khandker, Emran

    2015-01-01

    We present a new cladding design for photonic crystal fiber (PCF) on a decagonal structure to simultaneously achieve ultra-flattened large negative dispersion and ultrahigh birefringence. Numerical results confirm that the proposed PCFexhibits ultra-flattened large negative dispersion over the S ...

  20. Validation of molecular crystal structures from powder diffraction data with dispersion-corrected density functional theory (DFT-D)

    DEFF Research Database (Denmark)

    van de Streek, Jacco; Neumann, Marcus A

    2014-01-01

    In 2010 we energy-minimized 225 high-quality single-crystal (SX) structures with dispersion-corrected density functional theory (DFT-D) to establish a quantitative benchmark. For the current paper, 215 organic crystal structures determined from X-ray powder diffraction (XRPD) data and published...

  1. An exact linear dispersion relation for CRM instability

    International Nuclear Information System (INIS)

    Choyal, Y; Minami, K

    2011-01-01

    An exact self-consistent linear dispersion relation of a large orbit electron beam including two principles of cyclotron emission with oscillation frequencies above and below the relativistic electron frequency is derived and analyzed numerically for the first time in the literature. The two principles are cyclotron resonance maser (CRM) instability and Cherenkov instability in the azimuthal direction. Self-consistency in the formulation and inclusion of proper boundary conditions have removed the unphysical instability existing for infinitely large k z observed in conventional dispersion relations of CRM instability.

  2. A linearized dispersion relation for orthorhombic pseudo-acoustic modeling

    KAUST Repository

    Song, Xiaolei

    2012-11-04

    Wavefield extrapolation in acoustic orthorhombic anisotropic media suffers from wave-mode coupling and stability limitations in the parameter range. We introduce a linearized form of the dispersion relation for acoustic orthorhombic media to model acoustic wavefields. We apply the lowrank approximation approach to handle the corresponding space-wavenumber mixed-domain operator. Numerical experiments show that the proposed wavefield extrapolator is accurate and practically free of dispersions. Further, there is no coupling of qSv and qP waves, because we use the analytical dispersion relation. No constraints on Thomsen\\'s parameters are required for stability. The linearized expression may provide useful application for parameter estimation in orthorhombic media.

  3. Self-adjusting smart windows based on polymer-dispersed liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Cupelli, Daniela; Pasquale Nicoletta, Fiore; Vivacqua, Marco; Formoso, Patrizia [Dipartimento di Scienze Farmaceutiche, Universita della Calabria, 87036 Rende (CS) (Italy); Manfredi, Sabrina; De Filpo, Giovanni; Chidichimo, Giuseppe [Dipartimento di Chimica, Universita della Calabria, 87036 Rende (CS) (Italy)

    2009-11-15

    The control of sunlight can be achieved either by electrochromic or polymer-dispersed liquid crystal (PDLC) smart windows. We have recently shown that it is possible to homeotropically align fluid mixtures of low molecular mass liquid crystal with a negative dielectric anisotropy, and a liquid crystalline monomer, in order to obtain electrically switchable chromogenic devices. They are new materials useful for external glazing. In fact, they are not affected by the classical drawbacks of PDLCs. In this paper we present a new self-switchable glazing technology based on the light-controlled transmittance in a PDLC device. The self-adjusting chromogenic material, which we obtain, is able to self-increase its scattering as a function of the impinging light intensity. The relationship between the electro-optical response and the physical-chemical properties of the components has been also investigated. (author)

  4. Dispersion Relations for Electroweak Observables in Composite Higgs Models

    CERN Document Server

    Contino, Roberto

    2015-12-14

    We derive dispersion relations for the electroweak oblique observables measured at LEP in the context of $SO(5)/SO(4)$ composite Higgs models. It is shown how these relations can be used and must be modified when modeling the spectral functions through a low-energy effective description of the strong dynamics. The dispersion relation for the parameter $\\epsilon_3$ is then used to estimate the contribution from spin-1 resonances at the 1-loop level. Finally, it is shown that the sign of the contribution to the $\\hat S$ parameter from the lowest-lying spin-1 states is not necessarily positive definite, but depends on the energy scale at which the asymptotic behavior of current correlators is attained.

  5. Age--velocity-dispersion relation in the solar neighborhood

    Energy Technology Data Exchange (ETDEWEB)

    Carlberg, R.G.; Dawson, P.C.; Hsu, T.; VandenBerg, D.A.

    1985-07-15

    The age--velocity-dispersion relation for stars in the solar neighborhood is examined as an indicator of the dominant acceleration mechanism of the stars and the formation history of the local disk. Twarog's sample of F stars, for which ages and photometric distances can be determined, is combined with astrometric data to obtain tangential velocities of a set of stars with a large age range. The resulting age--velocity-dispersion relation rises fairly steeply for stars less than 6 Gyr old, thereafter becoming nearly constant with age. These data are consistent with a simple model in which no local disk is initially present, following which stars are born at a constant rate in time and heated by transient spiral waves. The corresponding age-metallicity relation complements this dynamical measure of the formation history of the disk. The use of new stellar models and a revised metallicity calibration leads to quantitative differences from previous work.

  6. The age-velocity-dispersion relation in the solar neighborhood

    Science.gov (United States)

    Carlberg, R. G.; Dawson, P. C.; Hsu, T.; Vandenberg, D. A.

    1985-07-01

    The age-velocity-dispersion relation for stars in the solar neighborhood is examined as an indicator of the dominant acceleration mechanism of the stars and the formation history of the local disk. Twarog's sample of F stars, for which ages and photometric distances can be determined, is combined with astrometric data to obtain tangential velocities of a set of stars with a large age range. The resulting age-velocity-dispersion relation rises fairly steeply for stars less than 6 Gyr old, thereafter becoming nearly constant with age. These data are consistent with a simple model in which no local disk is initially present, following which stars are born at a constant rate in time and heated by transient spiral waves. The corresponding age-metallicity relation complements this dynamical measure of the formation history of the disk. The use of new stellar models and a revised metallicity calibration leads to quantitative differences from previous work.

  7. Orientation dependence of dispersion and band gap of PIMNT single crystals

    Science.gov (United States)

    He, Chongjun; Chen, Hongbing; Wang, Jiming; Gu, Xiaorong; Wu, Tong; Liu, Youwen

    2018-01-01

    As piezoelectric materials, optical properties of xPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 single crystals were not perfectly known. Here refractive indices and optical transmission of 0.25Pb(In1/2Nb1/2)O3-0.42Pb(Mg1/3Nb2/3)O3- 0.33PbTiO3 (PIMNT) single crystal are investigated after poled along different directions. Cauchy dispersion equations of the refractive indices were obtained by least square fitting, which can be used to calculate the refractive indices in the low absorption wavelength range. After poled along [011] direction, the optical transmission of PIMNT single crystal is more than 65% above 0.5 μm, which is much higher than that of [001] and [111] directions. Energy band gap was obtained from absorption coefficient.

  8. Improved pion pion scattering amplitude from dispersion relation formalism

    International Nuclear Information System (INIS)

    Cavalcante, I.P.; Coutinho, Y.A.; Borges, J. Sa

    2005-01-01

    Pion-pion scattering amplitude is obtained from Chiral Perturbation Theory at one- and two-loop approximations. Dispersion relation formalism provides a more economic method, which was proved to reproduce the analytical structure of that amplitude at both approximation levels. This work extends the use of the formalism in order to compute further unitarity corrections to partial waves, including the D-wave amplitude. (author)

  9. Validation of molecular crystal structures from powder diffraction data with dispersion-corrected density functional theory (DFT-D).

    Science.gov (United States)

    van de Streek, Jacco; Neumann, Marcus A

    2014-12-01

    In 2010 we energy-minimized 225 high-quality single-crystal (SX) structures with dispersion-corrected density functional theory (DFT-D) to establish a quantitative benchmark. For the current paper, 215 organic crystal structures determined from X-ray powder diffraction (XRPD) data and published in an IUCr journal were energy-minimized with DFT-D and compared to the SX benchmark. The on average slightly less accurate atomic coordinates of XRPD structures do lead to systematically higher root mean square Cartesian displacement (RMSCD) values upon energy minimization than for SX structures, but the RMSCD value is still a good indicator for the detection of structures that deserve a closer look. The upper RMSCD limit for a correct structure must be increased from 0.25 Å for SX structures to 0.35 Å for XRPD structures; the grey area must be extended from 0.30 to 0.40 Å. Based on the energy minimizations, three structures are re-refined to give more precise atomic coordinates. For six structures our calculations provide the missing positions for the H atoms, for five structures they provide corrected positions for some H atoms. Seven crystal structures showed a minor error for a non-H atom. For five structures the energy minimizations suggest a higher space-group symmetry. For the 225 SX structures, the only deviations observed upon energy minimization were three minor H-atom related issues. Preferred orientation is the most important cause of problems. A preferred-orientation correction is the only correction where the experimental data are modified to fit the model. We conclude that molecular crystal structures determined from powder diffraction data that are published in IUCr journals are of high quality, with less than 4% containing an error in a non-H atom.

  10. Possible mechanism(s) behind recently observed effects of incorporating gold nanoparticles into a polymer-dispersed liquid crystal

    Science.gov (United States)

    Hinojosa, Alfonso; Sharma, Suresh

    2010-10-01

    Recently we reported that addition of relatively small concentrations of about 14-nm diameter gold nanoparticles (Au NPs) to a polymer-dispersed liquid crystal (PDLC) produces rather large changes in the electro-optical properties of the PDLC. For example, addition of Au NPs to PDLC microstructure lowers its threshold voltage by almost 50% and increases optical transmission in a manner that depends on NPs concentration and applied electric field.ootnotetextA. Hinojosa and S. C. Sharma, Applied Physics Letters, 97, 081114 (2010) In order to understand these observations, we have carried out electro-optical measurements on several PDLCs as functions of the polarization of the incident laser beam and applied electric field. In this presentation, we will discuss the results obtained from these experiments and suggest mechanism(s), which might explain NPs-induced changes in the electro-optical properties of PDLCs.

  11. Dispersion of gold nanoclusters in TMBPA-polycarbonate by a combination of thermal embedding and vapour-induced crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Kruse, J; Dolgner, K; Greve, H; Zaporojtchenko, V; Faupel, F [Technische Fakultaet der Christian-Albrechts-Universitaet zu Kiel, Lehrstuhl fuer Materialverbunde, Kaiserstr. 2, D-24143 Kiel (Germany)

    2006-12-07

    Gold nanoclusters can be dispersed into the surface of a bisphenol-A polycarbonate film by acetone vapour induced crystallization, an effect which has been demonstrated in a previous publication of our group. Gold nanoclusters were deposited by physical vapour deposition on an amorphous thin film of polycarbonate. After vapour induced crystallization these clusters were detected by depth profiling to be embedded into the surface, with a concentration maximum in a depth of approximately 100 nm. In this work, we replaced the BPA by the modified tetramethyl bisphenol-A polycarbonate, which shows a slower crystallization kinetics. A strong enhancement of the dispersion depth has been achieved by thermal pre-embedding of the clusters into the surface. Surface analysis by means of atomic force microscopy reflects the rearrangement of polymer material in the course of crystallization.

  12. Dispersion of gold nanoclusters in TMBPA-polycarbonate by a combination of thermal embedding and vapour-induced crystallization

    Science.gov (United States)

    Kruse, J.; Dolgner, K.; Greve, H.; Zaporojtchenko, V.; Faupel, F.

    2006-12-01

    Gold nanoclusters can be dispersed into the surface of a bisphenol-A polycarbonate film by acetone vapour induced crystallization, an effect which has been demonstrated in a previous publication of our group. Gold nanoclusters were deposited by physical vapour deposition on an amorphous thin film of polycarbonate. After vapour induced crystallization these clusters were detected by depth profiling to be embedded into the surface, with a concentration maximum in a depth of approximately 100 nm. In this work, we replaced the BPA by the modified tetramethyl bisphenol-A polycarbonate, which shows a slower crystallization kinetics. A strong enhancement of the dispersion depth has been achieved by thermal pre-embedding of the clusters into the surface. Surface analysis by means of atomic force microscopy reflects the rearrangement of polymer material in the course of crystallization.

  13. Investigation of a polymer-dispersed liquid crystal system by NMR diffusometry and relaxometry

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Mingxue

    2013-02-26

    Polymer-dispersed liquid crystals (PDLCs) are polymer composites containing a dispersion of liquid crystal droplets in polymer networks. PDLCs have attracted much attention due to their unique properties and potential usage. The properties of PDLCs depend on the degree of phase separation and the size of liquid crystal droplets. To investigate the structure will help us to better understand and optimize PDLCs.The main aim of this PhD thesis was to investigate PDLCs by NMR techniques. Diffusion constants and spin-lattice relaxation times in the laboratory (T{sub 1}) and rotating frame (T{sub 1{rho}}) were measured for PDLCs as well as precursor mixtures based on the trifunctional monomer trimethylolpropane triacrylate (TMPTA) and the commercial nematic mixture E7. The variation of the main dipolar splitting of {sup 1}H spectra with increasing temperature was analyzed to obtain the nematic-to-isotropic phase transition temperature and the nematic order parameter of E7 and, for comparison, the nematic liquid crystal 5CB.Diffusion constants in TMPTA/E7 mixtures, measured by pulsed-field gradient NMR, increase for both E7 and TMPTA as the mass fraction of E7 increases, due to the lower viscosity of E7. E7 in the PDLC diffuses more slowly than in the bulk because of the hindrance by the polymer matrix. T{sub 1} and T{sub 1{rho}} relaxation times in the liquid or liquid-crystalline phases of TMPTA and bulk E7 are higher than in the PDLC and the pure polymer, due to the lower mobility in the polymer samples. T{sub 1{rho}} in the PDLC is even shorter than in the pure polymer, indicating an anti-softening effect caused by E7 molecules. In bulk E7, the well-ordered rod-like molecules exhibit a unique H-C dipolar coupling, which leads to oscillations in the cross-polarization curve. However, in the PDLC, the anchoring effect at the boundary between the polymer and LC droplets disturbs the molecular order resulting in a smooth cross polarization curve.

  14. Investigation of a polymer-dispersed liquid crystal system by NMR diffusometry and relaxometry

    International Nuclear Information System (INIS)

    Tang, Mingxue

    2013-01-01

    Polymer-dispersed liquid crystals (PDLCs) are polymer composites containing a dispersion of liquid crystal droplets in polymer networks. PDLCs have attracted much attention due to their unique properties and potential usage. The properties of PDLCs depend on the degree of phase separation and the size of liquid crystal droplets. To investigate the structure will help us to better understand and optimize PDLCs.The main aim of this PhD thesis was to investigate PDLCs by NMR techniques. Diffusion constants and spin-lattice relaxation times in the laboratory (T 1 ) and rotating frame (T 1ρ ) were measured for PDLCs as well as precursor mixtures based on the trifunctional monomer trimethylolpropane triacrylate (TMPTA) and the commercial nematic mixture E7. The variation of the main dipolar splitting of 1 H spectra with increasing temperature was analyzed to obtain the nematic-to-isotropic phase transition temperature and the nematic order parameter of E7 and, for comparison, the nematic liquid crystal 5CB.Diffusion constants in TMPTA/E7 mixtures, measured by pulsed-field gradient NMR, increase for both E7 and TMPTA as the mass fraction of E7 increases, due to the lower viscosity of E7. E7 in the PDLC diffuses more slowly than in the bulk because of the hindrance by the polymer matrix. T 1 and T 1ρ relaxation times in the liquid or liquid-crystalline phases of TMPTA and bulk E7 are higher than in the PDLC and the pure polymer, due to the lower mobility in the polymer samples. T 1ρ in the PDLC is even shorter than in the pure polymer, indicating an anti-softening effect caused by E7 molecules. In bulk E7, the well-ordered rod-like molecules exhibit a unique H-C dipolar coupling, which leads to oscillations in the cross-polarization curve. However, in the PDLC, the anchoring effect at the boundary between the polymer and LC droplets disturbs the molecular order resulting in a smooth cross polarization curve.

  15. Effect of a Polymercaptan Material on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystal Films

    OpenAIRE

    Yujian Sun; Cuihong Zhang; Le Zhou; Hua Fang; Jianhua Huang; Haipeng Ma; Yi Zhang; Jie Yang; Lan-Ying Zhang; Ping Song; Yanzi Gao; Jiumei Xiao; Fasheng Li; Kexuan Li

    2016-01-01

    Polymer-dispersed liquid crystal (PDLC) films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found...

  16. Multiplexing storage using angular variation in a transmission holographic polymer dispersed liquid crystal

    International Nuclear Information System (INIS)

    Kim, Eun-Hee; Jung, Yeon-Gil

    2015-01-01

    Simultaneous angular multiplexing of transmission gratings in a holographic polymer dispersed liquid crystal (HPDLC) film as a function of resin and film compositions, irradiation intensity, and cell thickness has been studied by exposing the material to three coherent laser beams. It was found that the diffraction efficiency monotonically increases with irradiation intensity and cell gap, whereas a maximum of 43% is obtained at specific compositions of trimethylolpropane triacrylate (TMPTA)/N-vinylpyrrolidone (NVP) = 8/1 and polymer/LC = 65/35. The multiplexed gratings have been captured using SEM imaging and the reconstructed images using a charge-coupled device camera, showing successful reconstructed images of gratings. - Highlights: • Multiplex images were well recorded using simultaneous angular method. • The periodic structures of the LC and polymer regions were well prepared. • The angular selectivity was variable nevertheless fabrication by three beams. • The images were successfully reconstructed in gratings of same spot.

  17. Multiplexing storage using angular variation in a transmission holographic polymer dispersed liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun-Hee; Jung, Yeon-Gil, E-mail: jungyg@changwon.ac.kr

    2015-12-01

    Simultaneous angular multiplexing of transmission gratings in a holographic polymer dispersed liquid crystal (HPDLC) film as a function of resin and film compositions, irradiation intensity, and cell thickness has been studied by exposing the material to three coherent laser beams. It was found that the diffraction efficiency monotonically increases with irradiation intensity and cell gap, whereas a maximum of 43% is obtained at specific compositions of trimethylolpropane triacrylate (TMPTA)/N-vinylpyrrolidone (NVP) = 8/1 and polymer/LC = 65/35. The multiplexed gratings have been captured using SEM imaging and the reconstructed images using a charge-coupled device camera, showing successful reconstructed images of gratings. - Highlights: • Multiplex images were well recorded using simultaneous angular method. • The periodic structures of the LC and polymer regions were well prepared. • The angular selectivity was variable nevertheless fabrication by three beams. • The images were successfully reconstructed in gratings of same spot.

  18. Low loss and flat dispersion Kagome photonic crystal fiber in the terahertz regime

    Science.gov (United States)

    Rana, Sohel; Rakin, Adnan Siraj; Hasan, Md. Rabiul; Reza, Md. Salim; Leonhardt, Rainer; Abbott, Derek; Subbaraman, Harish

    2018-03-01

    A novel fiber design based on hexagonal shaped holes incorporated within the core of a Kagome lattice photonic crystal fiber (PCF) is presented. The modal properties of the proposed fiber are evaluated by using a finite element method (FEM) with a perfectly matched layer as boundary condition. Simulation results exhibit an ultra-low effective material loss (EML) of 0.029 cm-1 at an operating frequency of 1.3 THz with an optimized core diameter of 300 μm. A positive, low, and flat dispersion of 0.49 ± 0.06 ps/THz/cm is obtained within a broad frequency range from 1.00 to 1.76 THz. Other essential guiding features of the designed fiber such as power fraction and confinement loss are studied. The fabrication possibilities are also investigated to demonstrate feasibility for a wide range of terahertz applications.

  19. Transflective multiplexing of holographic polymer dispersed liquid crystal using Si additives

    Directory of Open Access Journals (Sweden)

    2011-01-01

    Full Text Available Morphology, grating formation dynamics and electro-optical performance of transflective multiplexing with holographic polymer dispersed liquid crystal (HPDLC were investigated in the presence of silica nanoparticles (Aerosil R812 (RS and modified Aerosil 200 (MS and silicon monomer (vinyltrimethoxy silane (VTMS by using three coherent laser beams. The addition of Si additive significantly augmented the diffraction efficiencies of transmission and reflection gratings due to the enhanced phase separation with large LC channels. The film was driven only with Si additives which are enriched at the polymer-LC interfaces. As the additive content increased, driving voltage decreased to a minimum of 30 V at 2.0 wt% VTMS. It was found that the interface modification and large droplet size are crucial to operate the film. Among the three types of Si additive, VTMS showed the highest electro-optical performance due to its low viscosity and high reactivity.

  20. Dual-frequency bistable reflective cholesteric liquid crystal displays based on chiral-flexoelectric polarisation dispersion

    Science.gov (United States)

    Outram, B. I.; Elston, S. J.

    2013-08-01

    A new approach to switching between states in reflective cholesteric liquid crystal displays is demonstrated that relies on the dispersion in the cholesteric material's dielectric properties due to flexoelectricity. Flexoelectric polarisation allows the device to be switched into a weakly scattering focal-conic state at low frequencies, while at higher frequencies the device is driven into the reflective Grandjean state. The non-conventional dual-frequency effect allows driving between states in both directions. The cross-over frequency can be as low as 300 Hz, orders of magnitude smaller than other dual-frequency effects. Devices of various reflective colours are demonstrated and have favourable contrast ratios, viewing angles, and switching behaviours at room temperature. The technique potentially affords a greater flexibility in surface alignment conditions, driving schemes, material parameters, and use of polymer networks in cholesteric devices than other switching methods.

  1. Reflection of light by anisotropic molecular crystals including exciton-polaritons and spatial dispersion.

    Science.gov (United States)

    Meskers, Stefan C J; Lakhwani, Girish

    2016-11-21

    A theory for the reflection of light by molecular crystals is described, which reproduces the minimum within the reflection band that is observed experimentally. The minimum in reflection is related to the excitation of polaritons in the crystal. The theory involves reformulation of the boundary conditions for electromagnetic waves at the interface between vacuum and material. The material is modeled by a cubic lattice of oriented Lorentz oscillators. By requiring uniformity of gauge of the electromagnetic potential across the interface between vacuum and the dipole lattice, the need for additional boundary conditions is obviated. The frequency separation between the maxima in reflectance on both sides of the minimum allows for the extraction of a plasma frequency. The plasma frequencies extracted from reflection spectra are compared to the plasma frequencies calculated directly from structural data on the crystals and the oscillator strengths of the constituent molecules. A good agreement between extracted and calculated plasma frequency is obtained for a set of 11 dye molecules.

  2. Estimation of Phonon Dispersion Relations Using Correlation Effects Among Thermal Displacements of Atoms

    Directory of Open Access Journals (Sweden)

    Y. Ishikawa

    2015-04-01

    Full Text Available Neutron diffraction measurement of powder α-Fe sample at 295 K was carried out at the high resolution powder diffractometer installed at Japan Proton Accelerator Research Complex (J-PARC. Crystal parameters were determined from Rietveld analysis. The correlation effects among thermal displacements of atoms were estimated from a generalized equation based on the results of fomer diffuse scattering analysis. The force constants among atoms were obtained using an equation for transforming of the correlation effects to force constants. The force constants and the crystal structure of α-Fe were used to estimate the phonon dispersion relations, phonon density of states, and specific heat by computer simulation. The obtained force constants among first-nearest-neighboring atoms is 2.3 eV/Å2 at 295 K and the specific heat is 185 meV/K at 150 K. The calculated phonon dispersion relations and specific heat of α-Fe are similar to those obtained from inelastic neutron scattering and specific heat measurements, respectively

  3. Electro-optic and thermo-optic and properties of phase separated polymer dispersed liquid crystal films

    Czech Academy of Sciences Publication Activity Database

    Malik, P.; Bubnov, Alexej M.; Raina, K.K.

    2008-01-01

    Roč. 494, č. 12 (2008), s. 242-251 ISSN 1542-1406 Institutional research plan: CEZ:AV0Z10100520 Keywords : polymer dispersed liquid crystals * electro-optics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.537, year: 2008

  4. Observables and dispersion relations in κ-Minkowski spacetime

    Science.gov (United States)

    Aschieri, Paolo; Borowiec, Andrzej; Pachoł, Anna

    2017-10-01

    We revisit the notion of quantum Lie algebra of symmetries of a noncommutative spacetime, its elements are shown to be the generators of infinitesimal transformations and are naturally identified with physical observables. Wave equations on noncommutative spaces are derived from a quantum Hodge star operator. This general noncommutative geometry construction is then exemplified in the case of κ-Minkowski spacetime. The corresponding quantum Poincaré-Weyl Lie algebra of in-finitesimal translations, rotations and dilatations is obtained. The d'Alembert wave operator coincides with the quadratic Casimir of quantum translations and it is deformed as in Deformed Special Relativity theories. Also momenta (infinitesimal quantum translations) are deformed, and correspondingly the Einstein-Planck relation and the de Broglie one. The energy-momentum relations (dispersion relations) are consequently deduced. These results complement those of the phenomenological literature on the subject.

  5. Relative toxicity of oil dispersants to Mytilus viridis and Macrobrachium idella

    Digital Repository Service at National Institute of Oceanography (India)

    DeSilva, C.; Row, A.

    There was a great variation in the relative toxicity of different oil dispersants. Dispersant IB 2/80 was most toxic and dispersant IB 11/80 was not lethal at the highest concentration tested. The ranking order of the emulsions (oil dispersant...

  6. On light propagation in premetric electrodynamics: the covariant dispersion relation

    International Nuclear Information System (INIS)

    Itin, Yakov

    2009-01-01

    The premetric approach to electrodynamics provides a unified description of a wide class of electromagnetic phenomena. In particular, it involves axion, dilaton and skewon modifications of the classical electrodynamics. This formalism also emerges when the non-minimal coupling between the electromagnetic tensor and the torsion of Einstein-Cartan gravity is considered. Moreover, the premetric formalism can serve as a general covariant background of the electromagnetic properties of anisotropic media. In the current paper, we study wave propagation in the premetric electrodynamics. We derive a system of characteristic equations corresponded to premetric generalization of the Maxwell equation. This singular system is characterized by the adjoint matrix which turns to be of a very special form-proportional to a scalar quartic factor. We prove that a necessary condition for the existence of a non-trivial solution of the characteristic system is expressed by a unique scalar dispersion relation. In the tangential (momentum) space, it determines a fourth-order light hypersurface which replaces the ordinary light cone of the standard Maxwell theory. We derive an explicit form of the covariant dispersion relation and establish its algebraic and physical origin.

  7. Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space

    International Nuclear Information System (INIS)

    Zahn, J.W.

    2006-12-01

    We study field theories on the noncommutative Minkowski space with noncommuting time. The focus lies on dispersion relations in quantized interacting models in the Yang-Feldman formalism. In particular, we compute the two-point correlation function of the field strength in noncommutative quantum electrodynamics to second order. At this, we take into account the covariant coordinates that allow the construction of local gauge invariant quantities (observables). It turns out that this does not remove the well-known severe infrared problem, as one might have hoped. Instead, things become worse, since nonlocal divergences appear. We also show that these cancel in a supersymmetric version of the theory if the covariant coordinates are adjusted accordingly. Furthermore, we study the Φ 3 and the Wess-Zumino model and show that the distortion of the dispersion relations is moderate for parameters typical for the Higgs field. We also discuss the formulation of gauge theories on noncommutative spaces and study classical electrodynamics on the noncommutative Minkowski space using covariant coordinates. In particular, we compute the change of the speed of light due to nonlinear effects in the presence of a background field. Finally, we examine the so-called twist approach to quantum field theory on the noncommutative Minkowski space and point out some conceptual problems of this approach. (orig.)

  8. Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space

    Energy Technology Data Exchange (ETDEWEB)

    Zahn, J.W.

    2006-12-15

    We study field theories on the noncommutative Minkowski space with noncommuting time. The focus lies on dispersion relations in quantized interacting models in the Yang-Feldman formalism. In particular, we compute the two-point correlation function of the field strength in noncommutative quantum electrodynamics to second order. At this, we take into account the covariant coordinates that allow the construction of local gauge invariant quantities (observables). It turns out that this does not remove the well-known severe infrared problem, as one might have hoped. Instead, things become worse, since nonlocal divergences appear. We also show that these cancel in a supersymmetric version of the theory if the covariant coordinates are adjusted accordingly. Furthermore, we study the {phi}{sup 3} and the Wess-Zumino model and show that the distortion of the dispersion relations is moderate for parameters typical for the Higgs field. We also discuss the formulation of gauge theories on noncommutative spaces and study classical electrodynamics on the noncommutative Minkowski space using covariant coordinates. In particular, we compute the change of the speed of light due to nonlinear effects in the presence of a background field. Finally, we examine the so-called twist approach to quantum field theory on the noncommutative Minkowski space and point out some conceptual problems of this approach. (orig.)

  9. Fast Pairwise Conversion of Supernova Neutrinos: A Dispersion Relation Approach.

    Science.gov (United States)

    Izaguirre, Ignacio; Raffelt, Georg; Tamborra, Irene

    2017-01-13

    Collective pair conversion ν_{e}ν[over ¯]_{e}↔ν_{x}ν[over ¯]_{x} by forward scattering, where x=μ or τ, may be generic for supernova neutrino transport. Depending on the local angular intensity of the electron lepton number carried by neutrinos, the conversion rate can be "fast," i.e., of the order of sqrt[2]G_{F}(n_{ν_{e}}-n_{ν[over ¯]_{e}})≫Δm_{atm}^{2}/2E. We present a novel approach to understand these phenomena: a dispersion relation for the frequency and wave number (Ω,K) of disturbances in the mean field of ν_{e}ν_{x} flavor coherence. Runaway solutions occur in "dispersion gaps," i.e., in "forbidden" intervals of Ω and/or K where propagating plane waves do not exist. We stress that the actual solutions also depend on the initial and/or boundary conditions, which need to be further investigated.

  10. Extremely large bandwidth and ultralow-dispersion slow light in photonic crystal waveguides with magnetically controllability

    DEFF Research Database (Denmark)

    Pu, Shengli; Wang, Haotian; Wang, Ning

    2013-01-01

    of the lattice and the light speed in vacuum, respectively). Simultaneously, the normalized delay-bandwidth product is relatively large and almost invariant with magnetic field strength. It is indicated that using magnetic fluid as one of the constitutive materials of the photonic crystal structures can enable......A line-defect waveguide within a two-dimensional magnetic-fluid-based photonic crystal with 45o-rotated square lattice is presented to have excellent slow light properties. The bandwidth centered at $$ \\lambda_{0} $$ = 1,550 nm of our designed W1 waveguide is around 66 nm, which is very large than...... the magnetically fine tunability of the slow light in online mode. The concept and results of this work may give a guideline for studying and realizing tunable slow light based on the external-stimulus-responsive materials....

  11. Evaluate the ability of PVP to inhibit crystallization of amorphous solid dispersions by density functional theory and experimental verify.

    Science.gov (United States)

    Wang, Bing; Wang, Dandan; Zhao, Shan; Huang, Xiaobin; Zhang, Jianbin; Lv, Yan; Liu, Xiaocen; Lv, Guojun; Ma, Xiaojun

    2017-01-01

    In this study, we used density functional theory (DFT) to predict polymer-drug interactions, and then evaluated the ability of poly (vinyl pyrrolidone) (PVP) to inhibit crystallization of amorphous solid dispersions by experimental-verification. Solid dispersions of PVP/resveratrol (Res) and PVP/griseofulvin (Gri) were adopted for evaluating the ability of PVP to inhibit crystallization. The density functional theory (DFT) with the B3LYP was used to calculate polymer-drug and drug-drug interactions. Fourier transform infrared spectroscopy (FTIR) was used to confirm hydrogen bonding interactions. Polymer-drug miscibility and drug crystallinity were characterized by the modulated differential scanning calorimetry (MDSC) and X-ray powder diffraction (XRD). The release profiles were studied to investigate the dissolution advantage. DFT results indicated that E PVP-Res >E Res-Res (E: represents hydrogen bonding energy). A strong interaction was formed between PVP and Res. In addition, Fourier transform infrared spectroscopy (FTIR) analysis showed hydrogen bonding formed between PVP and Res, but not between PVP and Gri. MDSC and XRD results suggested that 70-90wt% PVP/Res and PVP/Gri solid dispersions formed amorphous solid dispersions (ASDs). Under the accelerated testing condition, PVP/Res dispersions with higher miscibility quantified as 90/10wt% were more stable than PVP/Gri dispersions. The cumulative dissolution rate of 90wt% PVP/Res dispersions still kept high after 90days storage due to the strong interaction. However, the cumulative dissolution rate of PVP/Gri solid dispersions significantly dropped because of the recrystallization of Gri. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Optical parameters and dispersion behavior of potassium magnesium chloride sulfate single crystals doped with Co+2 ions.

    Science.gov (United States)

    Abu El-Fadl, A; Abd-Elsalam, A M

    2018-05-05

    Single crystals of potassium magnesium chloride sulfate (KMCS) doped with cobalt ions were grown by slow cooling method. Powder XRD study confirmed the monoclinic structure of the grown crystals. The functional group vibrations were checked through FTIR spectroscopy measurements. In optical studies, the absorbance behavior of the crystals and their optical energy gap were established by Tauc plot. The refractive index, the extinction coefficient and other optical constants were calculated for the grown crystals. The normal dispersion of the refractive index was analyzed according to single oscillator Sellmeier's model. The Urbach's rule was applied to analyze the localized states density in the forbidden gap. Copyright © 2018 Elsevier B.V. All rights reserved.

  13. Dispersion spectrum of acoustoelectric waves in 1D piezoelectric crystal coupled with 2D infinite network of capacitors

    Science.gov (United States)

    Kutsenko, A. A.; Shuvalov, A. L.; Poncelet, O.

    2018-01-01

    A one-dimensional piezoelectric crystal coupled through periodically embedded electrodes with a two-dimensional semi-infinite periodic network of capacitors is considered. The unit cell of the network contains two capacitors with capacitances C1 and C2 which are in parallel and in series, respectively, with the electrodes. The dispersion spectrum of the longitudinal acoustoelectric wave in the piezoelectric crystal coupled with the electric wave of potentials and charges in the network of capacitors is investigated. It is shown that when C1 and C2 are of the same sign, the dispersion spectrum consists of a discrete set of curves, for which the electric wave exponentially decays into the depth of the network of capacitors. In contrast, if C1 and C2 are of the opposite sign and |C1/C2|capacitors.

  14. Dispersion and density of states of phonons and electrons in an α-B12 crystal determined from first principles

    Science.gov (United States)

    Mavrin, B. N.; Reshetnyak, V. V.

    2017-07-01

    Using the DFT method, we study the phonon properties of an α-B12 rhombohedral crystal in the basis set of plane waves and its electronic structure in the localized basis set of Gaussians. It follows from the phonon dispersion that the crystal possesses a dynamical stability. The effective Born charges, the oscillator strengths, the transverse-longitudinal splitting, and the dielectric functions of dipole modes are calculated. We show that charge transfer from polar to equatorial atoms takes place in a B12 icosahedron, while B-B bonds have predominantly a covalent character. In the density of states of acoustic modes, we reveal a structure that can manifest itself in the spectra of disordered boron compounds. From the dispersion of electronic bands, the occurrence of an indirect energy gap follows. The overlap of partial densities implies the hybridization of s and p electronic states in boron atoms.

  15. Approximate Dispersion Relations for Waves on Arbitrary Shear Flows

    Science.gov (United States)

    Ellingsen, S. À.; Li, Y.

    2017-12-01

    An approximate dispersion relation is derived and presented for linear surface waves atop a shear current whose magnitude and direction can vary arbitrarily with depth. The approximation, derived to first order of deviation from potential flow, is shown to produce good approximations at all wavelengths for a wide range of naturally occuring shear flows as well as widely used model flows. The relation reduces in many cases to a 3-D generalization of the much used approximation by Skop (1987), developed further by Kirby and Chen (1989), but is shown to be more robust, succeeding in situations where the Kirby and Chen model fails. The two approximations incur the same numerical cost and difficulty. While the Kirby and Chen approximation is excellent for a wide range of currents, the exact criteria for its applicability have not been known. We explain the apparently serendipitous success of the latter and derive proper conditions of applicability for both approximate dispersion relations. Our new model has a greater range of applicability. A second order approximation is also derived. It greatly improves accuracy, which is shown to be important in difficult cases. It has an advantage over the corresponding second-order expression proposed by Kirby and Chen that its criterion of accuracy is explicitly known, which is not currently the case for the latter to our knowledge. Our second-order term is also arguably significantly simpler to implement, and more physically transparent, than its sibling due to Kirby and Chen.Plain Language SummaryIn order to answer key questions such as how the ocean surface affects the climate, erodes the coastline and transports nutrients, we must understand how waves move. This is not so easy when depth varying currents are present, as they often are in coastal waters. We have developed a modeling tool for accurately predicting wave properties in such situations, ready for use, for example, in the complex oceanographic computer models. Our

  16. High birefringence and near-zero dispersion photonic crystal fiber at the wavelength of 1.55μm

    Science.gov (United States)

    Song, Peng; Wu, Limin; Wang, Jing; Zhou, Cheng

    2016-03-01

    We investigate a photonic crystal fiber (PCF) which consists of squeezed triangle lattice and elliptical air holes. Birefringence and dispersion properties of this PCF have been numerically estimated by the supercell lattice method. Numerical results show that the birefringence is on the order of 10-2 over ultrabroad wavelength rang from1.3μm to 1.7μm and birefringence can be reached 1.71×10-2 at the operating wavelength of 1.55μm. It is also demonstrated that two near-zero dispersion of -1.75(ps/nm/km) (x-polarized mode) and-0.33(ps/nm/km) (y-polarized mode) at 1.55μm can be achieved. Morever, the fluctuations of the dispersion with fiber parameters are very small. The simulation results show that our proposed PCF are robust to fabrication imperfections.

  17. Existence of an isotropic point and birefringence dispersion study in (C2H5NH3)2CuCl4 crystal near its thermochromic phase transition

    Science.gov (United States)

    Fernandez, J.; Gomez Cuevas, A.; Arriandiaga, M. A.; Socias, C.; Tello, M. J.

    1985-04-01

    The anomalous optical dispersion and the existence of an isotropic point in the organic-inorganic double-halide (C2H5NH3)2CuCl4 crystal (in short EACuC) around its thermochromic low-temperature phase transition were investigated by means of birefringence, thermal expansion, and calorimetric measurements as well as by direct conoscopic and orthoscopic observations under polarized light. The birefringence dispersion data are analyzed using a simple two-oscillator model based on the optical band structure of EACuC. The model adjustable parameters are related with the oscillator strength and average positions, respectively. The thermal behavior of the involved parameters is compatible with the existence of the isotropic point below the thermochromic phase transition. These results, together with the optical extinction measurements and the domain pattern observations, suggest a complicated structural phase-transition sequence which is also discussed.

  18. Bose gas with generalized dispersion relation plus an energy gap

    Science.gov (United States)

    Solis, M. A.; Martinez, J. G.; Garcia, J.

    We report the critical temperature, the condensed fraction, the internal energy and the specific heat for a d-dimensional Bose gas with a generalized dispersion relation plus an energy gap, i.e., ɛ =ɛ0 for k = 0 and ɛ =ɛ0 + Δ +csks , for k > 0 , where ℏk is the particle momentum, ɛ0 the lowest particle energy, cs a constant with dimension of energy multiplied by a length to the power s > 0 . When Δ > 0 , a Bose-Einstein critical temperature Tc ≠ 0 exists for any d / s >= 0 at which the internal energy shows a peak and the specific heat shows a jump. The critical temperature and the specific heat jump increase as functions of the gap but they decrease as functions of d / s . Thermodynamic properties are ɛ0 independent since this is just a reference energy. For Δ = 0 we recover the results reported in Ref. [1]. V. C. Aguilera-Navarro, M. de Llano y M. A. Solís, Eur. J. Phys. 20, 177 (1999). We acknowledge partial support from Grants PAPIIT IN111613 and CONACyT 221030.

  19. Role of the Strength of Drug-Polymer Interactions on the Molecular Mobility and Crystallization Inhibition in Ketoconazole Solid Dispersions.

    Science.gov (United States)

    Mistry, Pinal; Mohapatra, Sarat; Gopinath, Tata; Vogt, Frederick G; Suryanarayanan, Raj

    2015-09-08

    The effects of specific drug-polymer interactions (ionic or hydrogen-bonding) on the molecular mobility of model amorphous solid dispersions (ASDs) were investigated. ASDs of ketoconazole (KTZ), a weakly basic drug, with each of poly(acrylic acid) (PAA), poly(2-hydroxyethyl methacrylate) (PHEMA), and polyvinylpyrrolidone (PVP) were prepared. Drug-polymer interactions in the ASDs were evaluated by infrared and solid-state NMR, the molecular mobility quantified by dielectric spectroscopy, and crystallization onset monitored by differential scanning calorimetry (DSC) and variable temperature X-ray diffractometry (VTXRD). KTZ likely exhibited ionic interactions with PAA, hydrogen-bonding with PHEMA, and weaker dipole-dipole interactions with PVP. On the basis of dielectric spectroscopy, the α-relaxation times of the ASDs followed the order: PAA > PHEMA > PVP. In addition, the presence of ionic interactions also translated to a dramatic and disproportionate decrease in mobility as a function of polymer concentration. On the basis of both DSC and VTXRD, an increase in strength of interaction translated to higher crystallization onset temperature and a decrease in extent of crystallization. Stronger drug-polymer interactions, by reducing the molecular mobility, can potentially delay the crystallization onset temperature as well as crystallization extent.

  20. Long wave dispersion relations for surface waves in a magnetically structured atmosphere

    International Nuclear Information System (INIS)

    Rae, I.C.; Roberts, B.

    1983-01-01

    A means of obtaining approximate dispersion relations for long wavelength magnetoacoustic surface waves propagating in a magnetically structured atmosphere is presented. A general dispersion relation applying to a wide range of magnetic profiles is obtained, and illustrated for the special cases of a single interface and a magnetic slab. In the slab geometry, for example, the dispersion relation contains both the even (sausage) and odd (kink) modes in one formalism

  1. Polypyrrole-magnetite dispersive micro-solid-phase extraction combined with ultraviolet-visible spectrophotometry for the determination of rhodamine 6G and crystal violet in textile wastewater.

    Science.gov (United States)

    Kamaruddin, Amirah Farhan; Sanagi, Mohd Marsin; Wan Ibrahim, Wan Aini; Md Shukri, Dyia S; Abdul Keyon, Aemi S

    2017-11-01

    Polypyrrole-magnetite dispersive micro-solid-phase extraction method combined with ultraviolet-visible spectrophotometry was developed for the determination of selected cationic dyes in textile wastewater. Polypyrrole-magnetite was used as adsorbent due to its thermal stability, magnetic properties, and ability to adsorb Rhodamine 6G and crystal violet. Dispersive micro-solid-phase extraction parameters were optimized, including sample pH, adsorbent amount, extraction time, and desorption solvent. The optimum polypyrrole-magnetite dispersive micro-solid phase-extraction conditions were sample pH 8, 60 mg polypyrrole-magnetite adsorbent, 5 min of extraction time, and acetonitrile as the desorption solvent. Under the optimized conditions, the polypyrrole-magnetite dispersive micro-solid-phase extraction with ultraviolet-visible method showed good linearity in the range of 0.05-7 mg/L (R 2  > 0.9980). The method also showed a good limit of detection for the dyes (0.05 mg/L) and good analyte recoveries (97.4-111.3%) with relative standard deviations textile wastewater samples where the concentration found was 1.03 mg (RSD ±7.9%) and 1.13 mg/L (RSD ± 4.6%) for Rhodamine 6G and crystal violet, respectively. It can be concluded that this method can be adopted for the rapid extraction and determination of dyes at trace concentration levels. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Analytical relation between effective mode field area and waveguide dispersion in microstructure fibers.

    Science.gov (United States)

    Moenster, Mathias; Steinmeyer, Günter; Iliew, Rumen; Lederer, Falk; Petermann, Klaus

    2006-11-15

    For optical fibers exhibiting a radially symmetric refractive index profile, there exists an analytical relation that connects waveguide dispersion and the Petermann-II mode field radius. We extend the usefulness of this relation to the nonradially symmetric case of microstructure fibers in the anomalous dispersion regime, yielding a simple relation between dispersion and effective mode field area. Assuming a Gaussian mode distribution, we derive a fundamental upper limit for the effective mode field area that is required to obtain a certain amount of anomalous waveguide dispersion. This relation is demonstrated to show excellent agreement for fiber designs suited for supercontinuum generation and soliton lasers in the near infrared.

  3. Compact dispersion relations for parametric instabilities of electromagnetic waves in magnetized plasmas

    International Nuclear Information System (INIS)

    Cohen, B.I.

    1987-01-01

    The existence of compact dispersion relations for parametric instabilities of coherent electromagnetic waves in magnetized plasmas is addressed here. In general, comprehensive dispersion relations for parametric instabilities in unmagnetized plasmas become more complicated in the presence of an applied time-independent magnetic field. This is demonstrated with a fluid perturbation theory. A compact dispersion relation for parametric instabilities in unmagnetized plasma is heuristically extended here to the case of a magnetized plasma. This dispersion relation gives the correct results in a variety of circumstances of interest in considering electron cyclotron heating applications

  4. [Effect of the crystallization conditions of tetracycline base on the properties of the powders and drug forms obtained. The dependence of the degree of dispersion of tetracycline base on the crystallization conditions].

    Science.gov (United States)

    Lin'kov, G I; Zhukovskaia, S A; Dzhabarov, D N; Nabokov, V S

    1977-09-01

    Characteristics of the powder dispersity of tetracycline base samples prepared by directed crystallization with variation of the process conditions were determined by the sedimentation method. It was found that the speed of the solution agitation had the maximum effect on the level and nature of the dispersity. The rate of the solution temperature and pH changing during the crystallization process had also a significant effect at low agitation speed.

  5. Three-particle physics and dispersion relation theory

    CERN Document Server

    Anisovich, A V; Matveev, M A; Nikonov, V A; Nyiri, J; Sarantsev, A V

    2013-01-01

    The necessity of describing three-nucleon and three-quark systems have led to a constant interest in the problem of three particles. The question of including relativistic effects appeared together with the consideration of the decay amplitude in the framework of the dispersion technique. The relativistic dispersion description of amplitudes always takes into account processes connected with the investigated reaction by the unitarity condition or by virtual transitions; in the case of three-particle processes they are, as a rule, those where other many-particle states and resonances are produced. The description of these interconnected reactions and ways of handling them is the main subject of the book.

  6. Assembly of disperse red 1 molecules in the channels of AlPO4-5 single crystals for second-harmonic generation

    NARCIS (Netherlands)

    Jiang, FY; Lu, WX; Zhai, JP; Ye, JT; Wong, GKL; Han, Xueyao; Tang, ZK

    2006-01-01

    Disperse red 1 (DR1) molecules have been successfully incorporated into the one-dimensional channels of AlPO4-5 single crystals by means of vapor-phase diffusion. Polarizing microscope and SHG results indicate that the DR1 molecules are well aligned in a preferred direction along the crystal

  7. Oil, oil dispersants and related substances in the marine environment

    Science.gov (United States)

    Gunkel, W.; Gassmann, G.

    1980-03-01

    Of all substances threatening life in the seas, oil has received by far the most attention from the public, administrators, politicians and scientists. The main reasons for this are: (1) even limited amounts of oil are easily visible; (2) oil can exert obvious negative effects, e. g. extensive damage to birds and other animals, impairment of the recreational value of beaches and marinas, losses in fisheries due to tainting of catches and rejection by the public of seafood from areas known to have been recently polluted. In addition, dramatic tanker accidents are widely publicized. During the last decade tens of thousands of papers have been published about the impact of oil on the marine environment, and we are well informed about most basic facts, such as input and fate of oil, toxicity to adult organisms and recolonization. Due to considerable sophistication of analytical techniques, especially the introduction of glass-capillary gas chromatography, we are well aware that recently formed biogenic hydrocarbons by far extend the input directly due to pollution. Large gaps exist in our knowledge about sedimentation and transport of weathered oil, natural degradation rates, and the flow of hydrocarbons through the food web. Relatively little is known about the influence of oil and dispersants upon complex ecosystems. The often mentioned suspicion of increased cancer probability in humans due to seafood contaminated by hydrocarbons has not been substantiated; in fact, it seems unlikely that such an effect exists. By far the greatest uncertainty about potential oil impact concerns possible negative effects of hydrocarbons on chemical communication mechanisms between organisms. Intensive studies of behaviour scientists working with concentrations far below the toxic level are needed in fisheries biology, zoology and botany. Most cases of oil contamination known thus far have been limited in space and time; the oil has turned out to be degradable by natural processes

  8. Analysis of holographic polymer-dispersed liquid crystals (HPDLCs) for tunable low frequency diffractive optical elements recording

    Science.gov (United States)

    Fernández, R.; Gallego, S.; Márquez, A.; Francés, J.; Martínez, F. J.; Pascual, I.; Beléndez, A.

    2018-02-01

    Holographic polymer dispersed liquid crystals (HPDLCs) are the result of the optimization of the photopolymer fabrication techniques. They are made by recording in a photopolymerization induced phase separation process (PIPS) in which the liquid crystal molecules diffuse to dark zones in the diffraction grating originated. Thanks to the addition of liquid crystal molecules to the composition, this material has a dynamic behavior by reorientation of the liquid crystal molecules applying an electrical field. In this sense, it is possible to use this material to make dynamic devices. In this work, we study the behavior of this material working in low frequencies with different spatial periods of blazed gratings, a sharp profile whose recording is possible thanks to the addition of a Holoeye LCoS-Pluto spatial light modulator with a resolution of 1920 × 1080 pixels (HD) and a pixel size of 8 × 8 μm2. This device allows us to have an accurate and dynamic control of the phase and amplitude of the recording beam.

  9. Illusion optics via one-dimensional ultratransparent photonic crystals with shifted spatial dispersions.

    Science.gov (United States)

    Yao, Zhongqi; Luo, Jie; Lai, Yun

    2017-12-11

    In this work, we propose that one-dimensional ultratransparent dielectric photonic crystals with wide-angle impedance matching and shifted elliptical equal frequency contours are promising candidate materials for illusion optics. The shift of the equal frequency contour does not affect the refractive behaviors, but enables a new degree of freedom in phase modulation. With such ultratransparent photonic crystals, we demonstrate some applications in illusion optics, including creating illusions of a different-sized scatterer and a shifted source with opposite phase. Such ultratransparent dielectric photonic crystals may establish a feasible platform for illusion optics devices at optical frequencies.

  10. Dispersion relations of the acoustic modes in divalent liquid metals

    Directory of Open Access Journals (Sweden)

    Inui Masanori

    2017-01-01

    Full Text Available Collective dynamics in liquid Ca and liquid Cd was studied by inelastic x-ray scattering (IXS. Using our experimental technique to prepare proper sample cells and high performance of an IXS beamline (BL35XU at SPring-8 in Japan, the dynamic structure factor with reasonable statistics was obtained for these divalent liquid metals. For both liquids, the dynamic structure factor at low Q exhibits a central peak with a shoulder or small hump clearly visible on each side, and the inelastic excitation energy determined using the model function composed of Lorentzian and the damped harmonic oscillator function disperses with increasing Q. The dispersion curves of these liquids were compared with that of the longitudinal acoustic phonon in each crystalline phase. From these results, clear difference in the interatomic interaction be- tween liquid Ca and liquid Cd was inferred.

  11. The use of dispersion relations to construct unified nucleon optical potentials

    International Nuclear Information System (INIS)

    Hodgson, P.E.

    1991-01-01

    The dispersion relations provide a simple and accurate way of parametrizing the optical potential for a particular nucleus over a range of energies. A method is proposed for obtaining a global nucleon optical potential incorporating the dispersion relations. (author). 9 refs, 3 figs

  12. Linear dispersion relation for the mirror instability in context of the gyrokinetic theory

    International Nuclear Information System (INIS)

    Porazik, Peter; Johnson, Jay R.

    2013-01-01

    The linear dispersion relation for the mirror instability is discussed in context of the gyrokinetic theory. The objective is to provide a coherent view of different kinetic approaches used to derive the dispersion relation. The method based on gyrocenter phase space transformations is adopted in order to display the origin and ordering of various terms

  13. Fivefold Symmetric Photonic Quasi-Crystal Fiber for Dispersion Compensation from S- to L-Band and Optimized at 1.55 μm

    Directory of Open Access Journals (Sweden)

    Sivacoumar Rajalingam

    2015-01-01

    Full Text Available A highly dispersive dual core quasi-periodic photonic crystal fiber is proposed for chromatic dispersion compensation. The dispersion for the dual concentric core fiber is optimized to compensate the chromatic dispersion with a high negative dispersion, accomplishing the communication bandwidth from S-band (1460 nm to L-band (1625 nm. By precise control of structural parameter we have achieved a maximum dispersion of −18,838 ps/nm-km with the phase matching wavelength centred around 1.55 μm. We also numerically investigate the influence of structural parameter and doping effects and its response on peak dispersion parameter.

  14. New method to determine the optical rotatory dispersion of inorganic crystals applied to some samples of Carpathian Quartz.

    Science.gov (United States)

    Dimitriu, Dan Gheorghe; Dorohoi, Dana Ortansa

    2014-10-15

    A new method to determine the optical rotatory dispersion (ORD) in the visible range, based on a channeled spectrum obtained with a uniax inorganic crystal introduced between two crossed polarizers with its optical axis parallel to the light propagation direction is detailed in this paper. When the studied inorganic crystals are transparent, this method permits the estimation of the optical rotatory dispersion in the visible range, for which the cheap polarizers are available. The speed of the measurements is very high, because the estimations are made from the channeled spectrum obtained for a single arrangement of the optical components. By using a computer, ORD is quickly determined for the visible range. The results obtained by this method for some Carpathian Quartz samples are consistent with those from literature. The proposed method can be also applied in UV and IR spectral ranges, when the anisotropic layers are transparent and the linearly polarized radiations can be obtained. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Improved description of the structural and optoelectronic properties of DNA/RNA nucleobase anhydrous crystals: Experiment and dispersion-corrected density functional theory calculations

    Science.gov (United States)

    da Silva, M. B.; Francisco, T. S.; Maia, F. F.; Caetano, E. W. S.; Fulco, U. L.; Albuquerque, E. L.; Freire, V. N.

    2017-08-01

    The development of low cost and environmentally friendly organic electronic/optoelectronic devices has attracted a lot of interest. The integration of DNA and RNA nucleobases to improve the performance of organic light-emitting diodes has been proposed recently [Gomez et al., Sci. Rep. 4, 7105 (2014), 10.1038/srep07105], notwithstanding limited experimental and theoretical information on the optoelectronic properties of DNA/RNA thin films. As a contribution to an improved understanding of DNA/RNA-based devices in the solid state, we have performed in this paper dispersion corrected density functional theory (DFT) and time-dependent DFT (TDDFT) calculations to obtain the optimized geometries, Kohn-Sham band structures and orbitals, charge distribution, optical absorption, Frenkel exciton binding energies, and complex dielectric functions of the five DNA/RNA nucleobase anhydrous crystals, namely cytosine, guanine, adenine, thymine, and uracil. Optical absorption measurements on DNA/RNA nucleobase powders were also performed for comparison with the simulations. An improvement on the local density approximation (LDA) description of the lattice parameter estimates was achieved considering the generalized gradient approach (GGA) with a semiempirical dispersion correction scheme in comparison with structural x-ray data found in the literature. Energy gap correction using the Δ-sol methodology provided a good agreement between theory and experimental estimates from our optical absorption data, greatly surpassing the quality of previous simulations. Effective masses for the carriers were also found, indicating that the guanine crystal as well as the cytosine one (although with some drawbacks) has potential applications in optoelectronics as a direct gap semiconductor, with the other nucleobases presenting either a semiconductor or an insulator character depending on the carrier type. The complex dielectric function exhibits a high degree of anisotropy for different states

  16. Relation of wave energy and momentum with the plasma dispersion relation in an inhomogeneous plasma

    International Nuclear Information System (INIS)

    Berk, H.L.; Pfirsch, D.

    1988-01-01

    The expressions for wave energy and angular momentum commonly used in homogeneous and near-homogeneous media is generalized to inhomogeneous media governed by a nonlocal conductivity tensor. The expression for wave energy applies to linear excitations in an arbitrary three-dimensional equilibrium, while the expression for angular momentum applies to linear excitations of azimuthally symmetric equilibria. The wave energy E-script/sub wave/ is interpreted as the energy transferred from linear external sources to the plasma if there is no dissipation. With dissipation, such a simple interpretation is lacking as energy is also thermally absorbed. However, for azimuthally symmetric equilibria, the expression for the wave energy in a frame rotating with a frequency ω can be unambiguously separated from thermal energy. This expression is given by E-script/sub wave/ -ωL/sub wave/ l, where L/sub wave/ is the wave angular momentum defined in the text and l the azimuthal wavenumber and it is closely related to the real part of a dispersion relation for marginal stability. The imaginary part of the dispersion is closely related to the energy input into a system. Another useful quantity discussed is the impedance form, which can be used for three-dimensional equilibrium without an ignorable coordinate and the expression is closely related to the wave impedance used in antenna theory. Applications to stability theory are also discussed

  17. Modelling aerosol processes related to the atmospheric dispersion of sarin.

    Science.gov (United States)

    Kukkonen, J; Riikonen, K; Nikmo, J; Jäppinen, A; Nieminen, K

    2001-08-17

    We have developed mathematical models for evaluating the atmospheric dispersion of selected chemical warfare agents (CWA), including the evaporation and settling of contaminant liquid droplets. The models and numerical results presented may be utilised for designing protection and control measures against the conceivable use of CWA's. The model AERCLOUD (AERosol CLOUD) was extended to treat two nerve agents, sarin and VX, and the mustard agent. This model evaluates the thermodynamical evolution of a five-component aerosol mixture, consisting of two-component droplets together with the surrounding three-component gas. We have performed numerical computations with this model on the evaporation and settling of airborne sarin droplets in characteristic dispersal and atmospheric conditions. In particular, we have evaluated the maximum radii (r(M)) of a totally evaporating droplet, in terms of the ambient temperature and contaminant vapour concentration. The radii r(M) range from approximately 15-80 microm for sarin droplets for the selected ambient conditions and initial heights. We have also evaluated deposition fractions in terms of the initial droplet size.

  18. Comparative investigation of methods to determine the group velocity dispersion of an endlessly single-mode photonic crystal fiber

    Science.gov (United States)

    Baselt, Tobias; Popp, Tobias; Nelsen, Bryan; Lasagni, Andrés. Fabián.; Hartmann, Peter

    2017-05-01

    Endlessly single-mode fibers, which enable single mode guidance over a wide spectral range, are indispensable in the field of fiber technology. A two-dimensional photonic crystal with a silica central core and a micrometer-spaced hexagonal array of air holes is an established method to achieve endless single-mode guidance. There are two possible ways to determine the dispersion: measurement and calculation. We calculate the group velocity dispersion GVD based on the measurement of the fiber structure parameters, the hole diameter and the pitch of a presumed homogeneous hexagonal array and compare the calculation with two methods to measure the wavelength-dependent time delay. We measure the time delay on a three hundred meter test fiber with a homemade supercontinuum light source, a set of bandpass filters and a fast detector and compare the results with a white light interferometric setup. To measure the dispersion of optical fibers with high accuracy, a time-frequency-domain setup based on a Mach-Zehnder interferometer is used. The experimental setup allows the determination of the wavelength dependent differential group delay of light travelling through a thirty centimeter piece of test fiber in the wavelength range from VIS to NIR. The determination of the GVD using different methods enables the evaluation of the individual methods for characterizing the endlessly single-mode fiber.

  19. Dispersion relations from the hard thermal loop effective action in a magnetic field

    CERN Document Server

    Elmfors, Per

    1995-01-01

    Dispersion relations for fermions at high temperature and in a background magnetic field are calculated in two different ways. First from a straightforward one-loop calculation where, in the weak field limit, we find an expression closely related to the standard dispersion relations in the absence of the magnetic field. Secondly, we derive the dispersion relations directly from the Hard Thermal Loop effective action, which allows for an exact solution (i.e. to all orders in the external field), up to the last numerical integrals.

  20. Surface-plasmon dispersion relation for the inhomogeneous charge-density medium

    International Nuclear Information System (INIS)

    Harsh, O.K.; Agarwal, B.K.

    1989-01-01

    The surface-plasmon dispersion relation is derived for the plane-bounded electron gas when there is an inhomogeneous charge-density distribution in the plasma. The hydrodynamical model is used. Both cphi and dcphi/dx are taken to be continuous at the surface of the slab, where cphi is the scalar potential. The dispersion relation is compared with the theoretical works of Stern and Ferrell and of Harsh and Agarwal. It is also compared with the observations of Kunz. A dispersion relation for the volume-plasmon oscillations is derived which resembles the well-known relation of Bohm and Pines

  1. Wandering stars: age-related habitat use and dispersal of Javan Hawk-eagles (Spizaetus bartelsi)

    NARCIS (Netherlands)

    Nijman, V.; Balen, van S.

    2003-01-01

    Natal dispersal and philopatry have rarely been studied in tropical forest raptors. Especially with respect to endangered species with fragmented distributions more knowledge of dispersal and age-related habitat preferences is needed for proper management. We conducted an island-wide study on

  2. Comparison of Forward Dispersion Relations with Experiments around 10 GeV

    DEFF Research Database (Denmark)

    Lautrup, B.; Møller-Nielsen, Peter; Olesen, P.

    1965-01-01

    no assumptions whatsoever about the unknown cross sections above 20 GeV. On account of the large systematic errors in the measured real parts, no definite conclusion can be drawn as to the validity of forward dispersion relations. In estimating the standard deviations in the dispersion integrals, a Monte Carlo...

  3. The complex dispersion relation of surface plasmon polaritons at gold/para-hexaphenylene interfaces

    DEFF Research Database (Denmark)

    Lemke, Christoph; Leißner, Till; Klick, Alwin

    2014-01-01

    Two-photon photoemission electron microscopy (2P-PEEM) is used to measure the real and imaginary part of the dispersion relation of surface plasmon polaritons at different interface systems. A comparison of calculated and measured dispersion data for a gold/vacuum interface demonstrates...

  4. Propagation losses in photonic crystal waveguides: Effects of band tail absorption and waveguide dispersion

    DEFF Research Database (Denmark)

    Rigal, F.; Joanesarson, Kristoffer Bitsch; Lyasota, A.

    2017-01-01

    Propagation losses in GaAs-based photonic crystal (PhC) waveguides are evaluated near the semiconductor band-edge by measuring the finesse of corresponding Ln cavities. This approach yields simultaneously the propagation losses and the mode reflectivity at the terminations of the cavities. We...... is important for the monolithic integration of light sources with such optical elements....

  5. Gamma-ray relative energy response of Ce: YAG crystal

    International Nuclear Information System (INIS)

    Zhang Jianhua; Zhang Chuanfei; Hu Mengchun; Peng Taiping; Wang Zhentong; Tang Dengpan; Zhao Guangjun

    2010-01-01

    Gamma-ray relative energy response of Ce: YAG crystal, which is important for pulsed γ-ray measurement, was studied in this work.The Ce: YAG crystal, which was developed at Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, was aligned point by point with γ-rays scattered from an industrial 60 Co line source. The γ-ray relative energy response was calculated using the mass attenuation coefficient. The results show that the numerical calculation method of γ-ray relative energy response is reliable, and the experimental method with multi-energy point γ-ray by Compton scattering is also feasible, that can be used for checking up correctness of the numerical calculation results. (authors)

  6. Preparation of a Thermally Light-Transmittance-Controllable Film from a Coexistent System of Polymer-Dispersed and Polymer-Stabilized Liquid Crystals.

    Science.gov (United States)

    Guo, Shu-Meng; Liang, Xiao; Zhang, Cui-Hong; Chen, Mei; Shen, Chen; Zhang, Lan-Ying; Yuan, Xiao; He, Bao-Feng; Yang, Huai

    2017-01-25

    Polymer-dispersed liquid crystal (PDLC) and polymer-stabilized liquid crystal (PSLC) systems are the two primary distinct systems in the field of liquid crystal (LC) technology, and they are differentiated by their unique microstructures. Here, we present a novel coexistent system of polymer-dispersed and polymer-stabilized liquid crystals (PD&SLCs), which forms a homeotropically aligned polymer network (HAPN) within the LC droplets after a microphase separation between the LC and polymer matrix and combines the advantages of both the PDLC and PSLC systems. Then, we prepare a novel thermally light-transmittance-controllable (TLTC) film from the PD&SLC system, where the transmittance can be reversibly changed through thermal control from a transparent to a light-scattering state. The film also combines the advantageous features of flexibility and a potential for large-scale manufacturing, and it shows significant promise in future applications from smart windows to temperature sensors.

  7. An efficient zero-order description of the fine structure in the infrared reflection band of cubic ionic crystals and the phonon-polariton dispersion using Lorentz gauge

    Science.gov (United States)

    Meskers, Stefan C. J.

    2018-03-01

    The reflection of infrared light by ionic crystals with cubic symmetry such as lithium fluoride, LiF, is analyzed in terms of phonon-polaritons. In contrast to the conventional view on phonon-polaritons that uses the Coulomb gauge and assumes a purely local dielectric response of the material, we here develop an alternative description making use of the Lorentz gauge. This involves retarded interactions between charges, implying a non-local response of the material to electromagnetic radiation. The resulting new phonon-polariton dispersion relation features polaritons with negative group velocity in the frequency range in between the transverse (ωT) and longitudinal frequency (ωL). By contrast, the conventional description predicts, in zero order, the absence of any propagating polaritons in the frequency interval between ωT and ωL. The new dispersion relation provides an efficient, zero-order description of the fine structure within the reststrahlen band of LiF. The local minimum near the middle of the reflectance band is due to excitation of a phonon-polariton whose energy and momentum matches that of the incoming photon. The Lorentz gauge description can also describe off-normal reflection and accounts for the experimentally observed widening of the reflection band with increasing angle of incidence.

  8. Relative Dispersion from a High-Resolution Coastal Model of the Adriatic Sea

    National Research Council Canada - National Science Library

    Haza, Angelique C; Poje, Andrew C; Ozgokmen, Tamay M; Martin, Paul

    2008-01-01

    Synthetic drifter trajectories computed from velocity data produced by a high-resolution NCOM model are used to investigate the scaling of relative dispersion and the distribution of finite-scale Lyapunov exponent (FSLE...

  9. A Neutron Study for Phonon Dispersion Relations in HgTe

    DEFF Research Database (Denmark)

    Kepa, H.; Gebicki, W.; Giebultowicz, T.

    1980-01-01

    Dispersion relations for acoustic phonons in mercury telluride in three high symmetry directions [111], [110] and [001] are presented. The eleven-parameter rigid-ion model is fitted to the experimental data....

  10. Two-crystal mid-infrared optical parametric oscillator for absorption and dispersion dual-comb spectroscopy.

    Science.gov (United States)

    Jin, Yuwei; Cristescu, Simona M; Harren, Frans J M; Mandon, Julien

    2014-06-01

    We present a femtosecond optical parametric oscillator (OPO) containing two magnesium-doped periodically poled lithium niobate crystals in a singly resonant ring cavity, pumped by two mode-locked Yb-fiber lasers. As such, the OPO generates two idler combs (up to 220 mW), covering a wavelength range from 2.7 to 4.2 μm, from which a mid-infrared dual-comb Fourier transform spectrometer is constructed. By detecting the heterodyning signal between the two idler beams a full broadband spectrum of a molecular gas can be observed over 250  cm(-1) within 70 μs with a spectral resolution of 15 GHz. The absorption and dispersion spectra of acetylene and methane have been measured around 3000  cm(-1), indicating that this OPO represents an ideal broadband mid-infrared source for fast chemical sensing.

  11. Holographic storage of three-dimensional image and data using photopolymer and polymer dispersed liquid crystal films

    International Nuclear Information System (INIS)

    Gao Hong-Yue; Liu Pan; Zeng Chao; Yao Qiu-Xiang; Zheng Zhiqiang; Liu Jicheng; Zheng Huadong; Yu Ying-Jie; Zeng Zhen-Xiang; Sun Tao

    2016-01-01

    We present holographic storage of three-dimensional (3D) images and data in a photopolymer film without any applied electric field. Its absorption and diffraction efficiency are measured, and reflective analog hologram of real object and image of digital information are recorded in the films. The photopolymer is compared with polymer dispersed liquid crystals as holographic materials. Besides holographic diffraction efficiency of the former is little lower than that of the latter, this work demonstrates that the photopolymer is more suitable for analog hologram and big data permanent storage because of its high definition and no need of high voltage electric field. Therefore, our study proposes a potential holographic storage material to apply in large size static 3D holographic displays, including analog hologram displays, digital hologram prints, and holographic disks. (special topic)

  12. Holographic storage of three-dimensional image and data using photopolymer and polymer dispersed liquid crystal films

    Science.gov (United States)

    Gao, Hong-Yue; Liu, Pan; Zeng, Chao; Yao, Qiu-Xiang; Zheng, Zhiqiang; Liu, Jicheng; Zheng, Huadong; Yu, Ying-Jie; Zeng, Zhen-Xiang; Sun, Tao

    2016-09-01

    We present holographic storage of three-dimensional (3D) images and data in a photopolymer film without any applied electric field. Its absorption and diffraction efficiency are measured, and reflective analog hologram of real object and image of digital information are recorded in the films. The photopolymer is compared with polymer dispersed liquid crystals as holographic materials. Besides holographic diffraction efficiency of the former is little lower than that of the latter, this work demonstrates that the photopolymer is more suitable for analog hologram and big data permanent storage because of its high definition and no need of high voltage electric field. Therefore, our study proposes a potential holographic storage material to apply in large size static 3D holographic displays, including analog hologram displays, digital hologram prints, and holographic disks. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474194, 11004037, and 61101176) and the Natural Science Foundation of Shanghai, China (Grant No. 14ZR1415500).

  13. Formation of holographic polymer-dispersed liquid crystal memory by angle-multiplexing recording for optically reconfigurable gate arrays.

    Science.gov (United States)

    Ogiwara, Akifumi; Watanabe, Minoru

    2015-12-20

    Formation of holographic polymer-dispersed liquid crystal (HPDLC) memory for an optically reconfigurable gate array is discussed for angle-multiplexing recording by controlling the laser interference exposure in LC composites. The successive laser illumination system to record the various configuration contexts at the specified region and angle in HPDLC memory is constructed by using the combination of a half-mirror and a photomask placed on the motorized stages under the control of a personal computer. The effect of laser exposure energy on the formation of holographic memory is investigated by measuring diffraction intensity as a function of exposure energy during the grating formation process and observing the internal grating structure by scanning electron microscopy. The optical reconfiguration in the gate-array VLSI is executed for configuration contexts of OR and NOR operations shown as logical operators that are reconstructed by laser irradiation at different incident angles for a specified region in the HPDLC memory.

  14. Morphological Tuning of the Plasmon Dispersion Relation in Dielectric-Loaded Nanofiber Waveguides

    DEFF Research Database (Denmark)

    Leißner, Till; Lemke, Christoph; Fiutowski, Jacek

    2013-01-01

    Understanding the impact of lateral mode confinement in plasmonic waveguides is of fundamental interest regarding potential applications in plasmonic devices. The knowledge of the frequency-wave vector dispersion relation provides the full information on electromagnetic field propagation in a wav......Understanding the impact of lateral mode confinement in plasmonic waveguides is of fundamental interest regarding potential applications in plasmonic devices. The knowledge of the frequency-wave vector dispersion relation provides the full information on electromagnetic field propagation...

  15. Integral and derivative dispersion relations for pp and $\\overline{p}p$ amplitudes

    CERN Document Server

    Alkin, A

    2010-01-01

    The methods of integral dispersion relations (IDR) and derivative dispersion relations (DDR) are applied for analysis of the data on pp and ¯pp total cross sections and ratios of real to imaginary part of elastic forward scattering amplitude. The models of pomeron behaving as triple, double and simple pole (with intercept larger than one) in the angular momentum plane are considered. Predictions of the models are given for the TOTEM measurements at 7 and 14 TeV.

  16. How cooperatively breeding birds identify relatives and avoid incest: New insights into dispersal and kin recognition.

    Science.gov (United States)

    Riehl, Christina; Stern, Caitlin A

    2015-12-01

    Cooperative breeding in birds typically occurs when offspring - usually males - delay dispersal from their natal group, remaining with the family to help rear younger kin. Sex-biased dispersal is thought to have evolved in order to reduce the risk of inbreeding, resulting in low relatedness between mates and the loss of indirect fitness benefits for the dispersing sex. In this review, we discuss several recent studies showing that dispersal patterns are more variable than previously thought, often leading to complex genetic structure within cooperative avian societies. These empirical findings accord with recent theoretical models suggesting that sex- biased dispersal is neither necessary, nor always sufficient, to prevent inbreeding. The ability to recognize relatives, primarily by learning individual or group-specific vocalizations, may play a more important role in incest avoidance than currently appreciated. © 2015 WILEY Periodicals, Inc.

  17. Misorientation related microstructure at the grain boundary in a nickel-based single crystal superalloy

    International Nuclear Information System (INIS)

    Huang, Ming; Zhuo, Longchao; Liu, Zhanli; Lu, Xiaogang; Shi, Zhenxue; Li, Jiarong; Zhu, Jing

    2015-01-01

    The mechanical properties of nickel-based single crystal superalloys deteriorate with increasing misorientation, thus the finished product rate of the casting of single crystal turbine airfoils may be reduced due to the formation of grain boundaries especially when the misorientation angle exceeds to some extent. To this day, evolution of the microstructures at the grain boundaries with misorientation and the relationship between the microstructures and the mechanical properties are still unclear. In this work a detailed characterization of the misorientation related microstructure at the grain boundary in DD6 single crystal superalloy has been carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques; the elemental distribution at the grain boundaries has been analyzed by energy dispersive (EDS) X-ray mapping; and the effect of precipitation of μ phases at the grain boundary on the mechanical property has been evaluated by finite element calculation. It is shown that the proportion of γ phase at the grain boundaries decreases, while the proportion of γ′ phase at the grain boundaries increases with increasing misorientation; the μ phase is precipitated at the grain boundaries when the misorientation angle exceeds about 10° and thus it could lead to a dramatic deterioration of the mechanical properties, as well as that the enrichment of Re and W gradually disappears as the misorientation angle increases. All these factors may result in the degradation of the mechanical properties at the grain boundaries as the misorientation increases. Furthermore, the finite element calculation confirms that precipitation of μ phases at the grain boundary is responsible for the significant deterioration of the mechanical properties when the misorientation exceeds about 10°. This work provides a physical imaging of the microstructure for understanding the relationship between the mechanical properties and the misorientation

  18. Effect of a Polymercaptan Material on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystal Films

    Directory of Open Access Journals (Sweden)

    Yujian Sun

    2016-12-01

    Full Text Available Polymer-dispersed liquid crystal (PDLC films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found that the weight ratio among acrylate monomers, thiol monomer PETMP and the polymercaptan Capcure 3-800 showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol-acrylate reaction and acrylate monomer polymerization reaction. While adding polymercaptans curing agent Capcure 3-800 with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol monomers.

  19. Effect of a Polymercaptan Material on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystal Films.

    Science.gov (United States)

    Sun, Yujian; Zhang, Cuihong; Zhou, Le; Fang, Hua; Huang, Jianhua; Ma, Haipeng; Zhang, Yi; Yang, Jie; Zhang, Lan-Ying; Song, Ping; Gao, Yanzi; Xiao, Jiumei; Li, Fasheng; Li, Kexuan

    2016-12-30

    Polymer-dispersed liquid crystal (PDLC) films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found that the weight ratio among acrylate monomers, thiol monomer PETMP and the polymercaptan Capcure 3-800 showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol-acrylate reaction and acrylate monomer polymerization reaction. While adding polymercaptans curing agent Capcure 3-800 with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol monomers.

  20. Effect of dielectric permittivity on the performance of polymer dispersed liquid crystal (PDLC) electrolyte dye-sensitized solar cells (DSSCs)

    Science.gov (United States)

    Kamarudin, Muhammad A. A.; Khan, Ammar A.; Qasim, Malik M.; Wilkinson, Timothy D.

    2016-09-01

    Dye-sensitized solar cells (DSSCs) are a type of organic solar cell often cited for their high efficiency and easy fabrication. Recent studies have shown that modification of the standard liquid electrolyte DSSC architecture by the changing one of the components or the addition of additives often results in the improvement in one of the photovoltaic parameters and hence the overall efficiency. Here we explore a dielectric liquid crystal material which is a known insulator but possesses a high degree of order and optical anisotropy. In the presence of an applied electric field, the equilibrium of positive and negative charges are displaced in opposite directions. In this work, different mixtures with different dielectric anisotropies ranging from negative, zero and positive are formulated. These mixtures are then used to prepare polymer dispersed liquid crystal (PDLC) electrolytes and subsequently DSSC devices based on these PDLC electrolytes are fabricated. The morphology of the PDLC is observed through polarizing optical microscopy (POM) and the electrical/photovoltaic characterizations are performed through current density-voltage (J-V) measurements and electrochemical impedance spectroscopy.

  1. Nano crystals-Related Synthesis, Assembly, and Energy Applications 2012

    International Nuclear Information System (INIS)

    Zou, B.; Yu, W.W.; Seo, J.; Zhu, T.; Hu, M.Z.

    2012-01-01

    During the past decades, nano crystals have attracted broad attention due to their unique shape- and size-dependent physical and chemical properties that differ drastically from their bulk counterparts. Hitherto, much effort has been dedicated to achieving rational controlling over the morphology, assembly, and related energy applications of the nano materials. Therefore, the ability to manipulate the morphology, size, and size distribution of inorganic nano materials is still an important goal in modern materials physics and chemistry. Especially, the world's demand for energy supply is causing a dramatic escalation of social and political unrest. Likewise, the environmental impact of the global climate change due to the combustion of fossil fuel is becoming increasingly alarming. These problems compel us to search for effective routes to build devices that can supply sustainable energy, with not only high efficiency but also environmental friendship. One of ways to relieve the energy crisis is to exploit devices based on renewable energy sources, such as solar energy and water power. Aiming at this exploration, the primary stage requires the design of appropriate strategies for the synthesis of high-quality nano crystals with respect to size uniformity and superior electrochemical performances. As a consequence, we organize the current special issue for Journal of Nano materials to provide the authors with a platform and readers with the latest achievements of nano crystals-related synthesis, assembly, and energy applications.

  2. Crystal chemistry of sartorite homologues and related sulfosalts

    DEFF Research Database (Denmark)

    Berlepsch, Peter; Makovicky, Emil; Balic-Zunic, Tonci

    2001-01-01

    sartorite homologues, sulfosalt, crystal chemistry, coordination polyhedra, bond-pairs, crankshaft chains......sartorite homologues, sulfosalt, crystal chemistry, coordination polyhedra, bond-pairs, crankshaft chains...

  3. Topology-optimized and dispersion-tailored photonic crystal slow-light devices

    DEFF Research Database (Denmark)

    Frandsen, Lars Hagedorn; Lavrinenko, Andrei; Borel, Peter Ingo

    2007-01-01

    not guarantee optimal solutions. The systematic design method based on topology optimization [1] allows creation of improved PhCW components with previously unseen low transmission losses, high operational bandwidths,and/or with wavelength selective functionalities. The method was originally developed...... distribution for the target mode and through a simple structural tuning of the waveguide geometry [3]. In this way, it is possible to realize a silicon-on-insulator PhCW with semi-slow light having a group velocity in the range ~(c0/15 – c0/100); vanishing, positive, or negative group velocity dispersion (GVD......); and low-loss propagation in a practical ~5-15 nm bandwidth. Such simple PhCW component may find widespread use in passive integrated circuits. The talk will present examples of topology-optimized PhCW components for broadband use and for narrowband use in the slow-light regime of PhCWs and exemplify how...

  4. Dispersion relation for localized magnetic polaritons propagating at ...

    Indian Academy of Sciences (India)

    Abstract. Localized magnetic polaritons are investigated in the systems consisting of two magnetic superlattices, coupled by a ferromagnetic contact layer. The general dis- persion relation for localized magnetic polaritons are derived in the framework of the electromagnetic wave theory in the Voigt geometry by the 'transfer' ...

  5. Ultrabroadband, Midinfrared Supercontinuum Generation in Dispersion Engineered As2Se3-Based Chalcogenide Photonic Crystal Fibers

    Directory of Open Access Journals (Sweden)

    Rim Cherif

    2013-01-01

    Full Text Available Small core As2Se3-based photonic crystal fibers (PCFs are accurately characterized for compact, high power, ultrabroadband, and coherent supercontinuum generation within few millimeters fiber length. Bandwidths of ~5.3 μm, 5 μm, and 3.2 μm were calculated for hole-to-hole spacings Λ= 3.5 μm, 4.5 μm, and 5.5 μm, respectively. The spectral broadening in the chalcogenide PCF is mainly caused by self-phase modulation and Raman-induced soliton self-frequency shift. The results show that small core As2Se3 PCFs are a promising candidate for mid-IR SCG up to ~8 μm.

  6. Nonlinear polarization dynamics in a weakly birefringent all-normal dispersion photonic crystal fiber : toward a practical coherent fiber supercontinuum laser

    DEFF Research Database (Denmark)

    Tu, Haohua; Liu, Yuan; Liu, Xiaomin

    2012-01-01

    Dispersion-flattened dispersion-decreased all-normal dispersion (DFDD-ANDi) photonic crystal fibers have been identified as promising candidates for high-spectral-power coherent supercontinuum (SC) generation. However, the effects of the unintentional birefringence of the fibers on the SC......−5 profoundly affects the SC generation in a DFDD-ANDi photonic crystal fiber. Conventional simulations based on the scalar generalized nonlinear Schrödinger equation (GNLSE) fail to reproduce the prominent observed features of the SC generation in a short piece (9-cm) of this fiber. However, these features can...... be qualitatively or semi-quantitatively understood by the coupled GNLSE that takes into account the form-birefringence. The nonlinear polarization effects induced by the birefringence significantly distort the otherwise simple spectrotemporal field of the SC pulses. We therefore propose the fabrication...

  7. Dispersion relation for long-wave neutrons and the possibility of its precise experimental verification

    International Nuclear Information System (INIS)

    Frank, A.I.; Nosov, V.G.

    1995-01-01

    Modern theoretical concepts concerning the dispersion relation for slow neutrons in matter are considered. The generally accepted optical-potential model is apparently not quite accurate and should be supplemented with some small corrections in the energy range attainable in experiments. For ultracold neutrons, these corrections are related to the proximity of the applicability boundary of the theory; for cold neutrons, these corrections are due to correlations in the positions of scatters. The accuracy of existing experiments is insufficient for confirmation or refutation these conclusions. A precision experiment is proposed to verify the dispersion relation for long-wave neutrons. 30 refs., 3 figs

  8. General dispersion and dissipation relations in a one-dimensional viscoelastic lattice

    International Nuclear Information System (INIS)

    Wang Wenqiang; Yu Jidong; Tang Zhiping

    2008-01-01

    We derive the general dispersion and dissipation relations for a one-dimensional viscoelastic lattice, demonstrate the relevance of these relations to viscoelastic fracture and phase transition, and show a procedure to determine the suitable mesh size in numerical simulation of stress waves propagating in viscoelastic continuum

  9. The general dispersion relation of induced streaming instabilities in quantum outflow systems

    Directory of Open Access Journals (Sweden)

    H. Mehdian

    2015-11-01

    Full Text Available In this manuscript the dispersion relations of streaming instabilities, by using the unique property (neutralized in charge and current by default of plasma shells colliding, have been generalized and studied. This interesting property for interpenetrating beams enables one to find the general dispersion relations without any restrictions used in the previous works in this area. In our previous work [H. Mehdian et al., ApJ. 801, 89 (2015], employing the plasma shell concept and boost frame method, the general dispersion relation for filamentation instability has been derived in the relativistic classical regime. But in this paper, using the above mentioned concepts, the general dispersion relations (for each of streaming instabilities, filamentation, two-stream and multi-stream in the non-relativistic quantum regime have been derived by employing the quantum fluid equations together with Maxwell equations. The derived dispersion relations enable to describe any arbitrary system of interacting two and three beams, justified neutralization condition, by choosing the inertial reference frame embedded on the one of the beams. Furthermore, by the numerical and analytical study of these dispersion relations, many new features of streaming instabilities (E.g. their cut-off wave numbers and growth rates in terms of all involved parameters have been illustrated. The obtained results in this paper can be used to describe many astrophysical systems and laboratory astrophysics setting, such as collision of non-parallel plasma shells over a background plasma or the collision of three neutralized plasma slabs, and justifying the many plasma phenomena such as particle accelerations and induced fields.

  10. NIR-Vis-UV Light-Responsive Actuator Films of Polymer-Dispersed Liquid Crystal/Graphene Oxide Nanocomposites.

    Science.gov (United States)

    Cheng, Zhangxiang; Wang, Tianjie; Li, Xiao; Zhang, Yihe; Yu, Haifeng

    2015-12-16

    To take full advantage of sunlight for photomechanical materials, NIR-vis-UV light-responsive actuator films of polymer-dispersed liquid crystal (PDLC)/graphene oxide (GO) nanocomposites were fabricated. The strategy is based on phase transition of LCs from nematic to isotropic phase induced by combination of photochemical and photothermal processes in the PDLC/GO nanocomposites. Upon mechanical stretching of the film, both topological shape change and mesogenic alignment occurred in the separated LC domains, enabling the film to respond to NIR-vis-UV light. The homodispersed GO flakes act as photoabsorbent and nanoscale heat source to transfer NIR or VIS light into thermal energy, heating the film and photothermally inducing phase transition of LC microdomains. By utilizing photochemical phase transition of LCs upon UV-light irradiation, one azobenzene dye was incorporated into the LC domains, endowing the nanocomposite films with UV-responsive property. Moreover, the light-responsive behaviors can be well-controlled by adjusting the elongation ratio upon mechanical treatment. The NIR-vis-UV light-responsive PDLC/GO nanocomposite films exhibit excellent properties of easy fabrication, low-cost, and good film-forming and mechanical features, promising their numerous applications in the field of soft actuators and optomechanical systems driven directly by sunlight.

  11. Fabrication of flexible polymer dispersed liquid crystal films using conducting polymer thin films as the driving electrodes

    International Nuclear Information System (INIS)

    Kim, Yang-Bae; Park, Sucheol; Hong, Jin-Who

    2009-01-01

    Conducting polymers exhibit good mechanical and interfacial compatibility with plastic substrates. We prepared an optimized coating formulation based on poly(3,4-ethylenedioxythiophene) (PEDOT) and 3-(trimethoxysilyl)propyl acrylate and fabricated a transparent electrode on poly(ethylene terephthalate) (PET) substrate. The surface resistances and transmittance of the prepared thin films were 500-600 Ω/□ and 87% at 500 nm, respectively. To evaluate the performance of the conducting polymer electrode, we fabricated a five-layer flexible polymer-dispersed liquid crystal (PDLC) device as a PET-PEDOT-PDLC-PEDOT-PET flexible film. The prepared PDLC device exhibited a low driving voltage (15 VAC), high contrast ratio (60:1), and high transmittance in the ON state (60%), characteristics that are comparable with those of conventional PDLC film based on indium tin oxide electrodes. The fabrication of conducting polymer thin films as the driving electrodes in this study showed that such films can be used as a substitute for an indium tin oxide electrode, which further enhances the flexibility of PDLC film

  12. Design and fabrication of a projection display using optically addressed polymer-dispersed liquid crystal light valves

    Science.gov (United States)

    Kikuchi, Hiroshi; Fujii, Takanori; Kawakita, Masahiro; Fujikake, Hideo; Takizawa, Kuniharu

    2000-03-01

    A prototype projection display consisting of optically addressed polymer-dispersed liquid crystal (PDLC) light valves and a schlieren optics is designed, built, and evaluated. This projection display which controls light by a scattering effect in the PDLC film, can be configured without requiring a polarizer and can create a brighter high-definition picture display with which high optical efficiency is possible. The relationship between the contrast ratio and the optical efficiency of a schlieren projection system is discussed. To design a projection display with both high brightness and a high contrast ratio, the scattering characteristics of a reflection-mode PDLC cell is evaluated and the optical efficiency of the total projection system is studied using a simple model with perfect diffusion of a light source. Using these results, we design and prototype PDLC light valves for a full-color display and construct a projection display. We succeed in displaying pictures with a contrast ratio of 80:1 and a brightness greater than 1800 ANSI lumens.

  13. The role of London dispersion interactions in strong and moderate intermolecular hydrogen bonds in the crystal and in the gas phase

    Science.gov (United States)

    Katsyuba, Sergey A.; Vener, Mikhail V.; Zvereva, Elena E.; Brandenburg, J. Gerit

    2017-03-01

    Two variants of density functional theory computations have been applied to characterization of hydrogen bonds of the 1-(2-hydroxylethyl)-3-methylimidazolium acetate ([C2OHmim][OAc]), i.e. with and without inclusion of dispersion interactions. A comparison of the results demonstrates that London dispersion interactions have very little impact on the energetical, geometrical, infrared spectroscopic and electron density parameters of charge-assisted intermolecular hydrogen bonds functioning both in the crystal of the [C2OHmim][OAc] and in the isolated [C2OHmim]+ [OAc]- ion pairs.

  14. On the detection of dispersion in the head-related transfer function

    Science.gov (United States)

    Constan, Zachary A.; Hartmann, William M.

    2003-08-01

    Because of dispersion in head-related transfer functions (HRTFs), the interaural time difference (ITD) varies with frequency. This physical effect ought to have consequences for the size or shape of the auditory image of broadband noise because different frequency regions of the noise have different ITDs. However, virtual reality experiments suggest that human listeners are insensitive to head-related dispersion. The experiments of this article test that suggestion by experiments that isolate dispersion from amplitude effects in the HRTF and attempt to optimize the opportunity for detecting it. Nevertheless, the experiments find that the only effect of dispersion is to shift the lateralization of the auditory image. This negative result is explained in terms of the cross-correlation function for head-dispersed noise. Although the broad-band cross-correlation function differs considerably from 1.0, the cross-correlation functions within bands characteristic of auditory filters do not. A detailed study of the lateralization shifts show that the experimental shifts can be successfully calculated as an average of stimulus ITDs as weighted by Raatgever's frequency-weighting function (Thesis, Delft, The Netherlands, 1980).

  15. The Analytical Form of the Dispersion Equation of Elastic Waves in Periodically Inhomogeneous Medium of Different Classes of Crystals

    Directory of Open Access Journals (Sweden)

    Nurlybek A. Ispulov

    2017-01-01

    Full Text Available The investigation of thermoelastic wave propagation in elastic media is bound to have much influence in the fields of material science, geophysics, seismology, and so on. The heat conduction equations and bound equations of motions differ by the difficulty level and presence of many physical and mechanical parameters in them. Therefore thermoelasticity is being extensively studied and developed. In this paper by using analytical matrizant method set of equation of motions in elastic media are reduced to equivalent set of first-order differential equations. Moreover, for given set of equations, the structure of fundamental solutions for the general case has been derived and also dispersion relations are obtained.

  16. Dispersion relation analysis of the neutral kaon regeneration amplitude in carbon

    CERN Document Server

    Angelopoulos, Angelos; Locher, M P; Markushin, V E; Aslanides, Elie; Backenstoss, Gerhard; Bargassa, P; Behnke, O; Benelli, A; Bertin, V; Blanc, F; Bloch, P; Carlson, P J; Carroll, M; Cawley, E; Chertok, M B; Danielsson, M; Dejardin, M; Derré, J; Ealet, A; Eleftheriadis, C; Faravel, L; Festcher, W; Fidecaro, Maria; Filipcic, A; Francis, D; Fry, J; Gabathuler, Erwin; Gamet, R; Gerber, H J; Go, A; Haselden, A; Hayman, P J; Henry-Coüannier, F; Hollander, R W; Jon-And, K; Kettle, P R; Kokkas, P; Kreuger, R; Le Gac, R; Leimgruber, F; Mandic, I; Manthos, N; Marel, Gérard; Mikuz, M; Miller, J; Montanet, François; Müller, A; Nakada, Tatsuya; Pagels, B; Papadopoulos, I M; Pavlopoulos, P; Polivka, G; Rickenbach, R; Roberts, B L; Ruf, T; Schäfer, M; Schaller, L A; Schietinger, T; Schopper, A; Tauscher, Ludwig; Thibault, C; Touchard, F; Touramanis, C; van Eijk, C W E; Vlachos, S; Weber, P; Wigger, O; Wolter, M; Zavrtanik, D; Zimmerman, D

    1999-01-01

    We apply a forward dispersion relation to the regeneration amplitude for kaon scattering on /sup 12/C using all available data. The CPLEAR data at low energies allow the determination of the net contribution from the subthreshold $9 region which turns out to be much smaller than earlier evaluations, solving a long standing puzzle. (29 refs).

  17. Dispersion relation for Bernstein waves using a new transformation for the modified Bessel function

    International Nuclear Information System (INIS)

    Sato, Masumi

    1985-01-01

    Aitken's or Shanks' transformation of the exponent-modified Bessel function produces better approximations. Dispersion relations for the hybrid and Bernstein waves using these provide better thermal and parallel wavenumber corrections. They also predict more closely the evolution and mode-conversion of these waves. (author)

  18. Sensorial analysis of polysaccharide-gelled protein particle dispersions in relation to lubrication and viscosity properties

    NARCIS (Netherlands)

    Chojnicka-Paszun, A.; Doussinault, S.; Jongh, de H.H.J.

    2014-01-01

    In this work polysaccharide-protein gel particle dispersions were studied to identify relation between sensorial responses and their bulk rheological and tribological properties. Sensory analysis was performed by a trained panel using QDA to evaluate distinct mouth-feel perception. Attributes such

  19. Dispersion relations for stationary light in one-dimensional atomic ensembles

    DEFF Research Database (Denmark)

    Lakoupov, Ivan; Ott, Johan Raunkjær; Chang, Darrick E

    2016-01-01

    We investigate the dispersion relations for light coupled to one-dimensional ensembles of atoms with different level schemes. The unifying feature of all the considered setups is that the forward and backward propagating quantum fields are coupled by the applied classical drives such that the gro...

  20. Dispersion relation for elastic electron-hydrogen atom forward scattering amplitude

    International Nuclear Information System (INIS)

    Kuchiev, M.Yu.; Amusia, M.Ya.

    1978-01-01

    The elastic e+H forward scattering amplitude is an analytical function in the complex energy E plane and has two cuts on the real axis: 0 < E < infinity and -infinity < E < -B, B being the hydrogen ionization potential. The e+H dispersion relation contains two integrals over the right and left cuts. (Auth.)

  1. Dispersion Relation of an OH-Stretching Vibration from Inelastic X-Ray Scattering

    Science.gov (United States)

    Winkler, Björn; Friedrich, Alexandra; Wilson, Dan J.; Haussühl, Eiken; Krisch, Michael; Bosak, Alexei; Refson, Keith; Milman, Victor

    2008-08-01

    We show that recent advances now allow us to measure the wave vector dependence of OH-stretching frequencies at energies around 400 meV by inelastic x-ray scattering using ID28@ESRF. We found a large, unexpected dispersion when we measured the dispersion relations of the hydrogen stretching frequencies of diaspore, α-AlOOH, where the hydrogen atoms participate in a hydrogen bond of intermediate strength. We can account for this behavior with density functional perturbation theory calculations and a simple model based on H-H interactions.

  2. Efficient approximations of dispersion relations in optical waveguides with varying refractive-index profiles.

    Science.gov (United States)

    Li, Yutian; Zhu, Jianxin

    2015-05-04

    In this paper we consider the problem of computing the eigen-modes for the varying refractive-index profile in an open waveguide. We first approximate the refractive-index by a piecewise polynomial of degree two, and the corresponding Sturm-Liouville problem (eigenvalue problem) of the Helmholtz operator in each layer can be solved analytically by the Kummer functions. Then, analytical approximate dispersion equations are established for both TE and TM cases. Furthermore, the approximate dispersion equations converge fast to the exact ones for the continuous refractive-index function as the maximum value of the subinterval sizes tends to zero. Suitable numerical methods, such as Müller's method or the chord secant method, may be applied to the dispersion relations to compute the eigenmodes. Numerical simulations show that our method is very practical and efficient for computing eigenmodes.

  3. Chiral symmetry and dispersion relations: from $\\pi \\pi$ scattering to hadronic light-by-light.

    CERN Multimedia

    CERN. Geneva

    2018-01-01

    Chiral symmetry provides strong constraints on hadronic matrix elements at low energy, which are most efficiently derived with chiral perturbation theory. As an effective quantum field theory the latter also accounts for rescattering or unitarity effects, albeit only perturbatively, via the loop expansion. In cases where rescattering effects are important it becomes necessary to go beyond the perturbative expansion, e.g. by using dispersion relations. A matching between the chiral and the dispersive representation provides in several cases results of high precision. I will discuss this approach with the help of a few examples, like $\\pi \\pi$ scattering (which has been tested successfully by CERN experiments like NA48/2 and DIRAC), $\\eta \\to 3 \\pi$ and the hadronic light-by-light contribution to $(g-2)_\\mu$. For the latter quantity the implementation of the dispersive approach has opened up the way to a model-independent calculation and the concrete possibility to significantly reduce the theoretical uncertain...

  4. Phonon dispersion relation in zircon, ZrSiO4 using inelastic neutron scattering at a pulsed neutron source

    International Nuclear Information System (INIS)

    Mittal, R.; Chaplot, S.L.; Parthasarathy, R.; Bull, M.J.; Harris, M.J.

    2000-01-01

    The coherent inelastic neutron scattering technique is used for the measurements of phonon dispersion relation in a geophysically important mineral zircon using PRISMA spectrometer as ISIS, UK. Lattice dynamical calculations of the phonon dispersion relation are carried out using a shell model. The one-phonon structure factors are calculated for selecting the Bragg points for the measurements and assignment of phonons to different branches. The calculations are in good agreement with the measured phonon dispersion relation. (author)

  5. Inclusions related to catalyst and medium for transmitting pressure in diamond single crystals grown at high temperature and high pressure from the Fe-C system

    International Nuclear Information System (INIS)

    Yin Longwei; Li Musen; Hao Zhaoyin; Zhang Jiongfa

    2001-01-01

    Inclusion entrapment in a crystal is one of the most important characteristics for the crystal growth technique from solution. Diamond single crystals grown from the Fe-C system at high temperature-high pressure usually contain inclusions related to the molten catalyst and the medium (pyrophyllite) for transmitting pressure. During the growth of the diamond, the inclusions are trapped by the growth front or are formed through reaction between the contaminants trapped in the diamond. In the present article, the inclusions related to the catalyst and pyrophyllite were systemically examined by transmission electron microscopy. The chemical composition and crystal structure of the inclusions were, for the first time, determined by selected area electron diffraction pattern combined with energy dispersive x-ray spectrometry. It was shown that the inclusions are mainly composed of orthorhombic Fe 3 C, orthorhombic FeSi 2 , hexagonal SiO 2 and face-centred cubic SiC. (author)

  6. The nonlinear effects on the characteristics of gravity wave packets: dispersion and polarization relations

    Directory of Open Access Journals (Sweden)

    S.-D. Zhang

    2000-10-01

    Full Text Available By analyzing the results of the numerical simulations of nonlinear propagation of three Gaussian gravity-wave packets in isothermal atmosphere individually, the nonlinear effects on the characteristics of gravity waves are studied quantitatively. The analyses show that during the nonlinear propagation of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, though nonlinear effects exist, the time variations of the frequencies of gravity wave packets are close to those derived from the dispersion relation and the amplitude and phase relations of wave-associated disturbance components are consistent with the predictions of the polarization relation of gravity waves. This indicates that the dispersion and polarization relations based on the linear gravity wave theory can be applied extensively in the nonlinear region.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides

  7. Solvent-shift strategy to identify suitable polymers to inhibit humidity-induced solid-state crystallization of lacidipine amorphous solid dispersions.

    Science.gov (United States)

    Sun, Mengchi; Wu, Chunnuan; Fu, Qiang; Di, Donghua; Kuang, Xiao; Wang, Chao; He, Zhonggui; Wang, Jian; Sun, Jin

    2016-04-30

    The solvent-shift strategy was used to identify appropriate polymers that inhibit humidity-induced solid-state crystallization of amorphous solid dispersions (ASDs). Lacidipine with the polymers, PVP-K30, HPMC-E5 or Soluplus, were combined to form amorphous solid dispersions prepared by solvent evaporation. The formulations were characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and Fourier-transform infrared spectroscopy (FT-IR) and were subjected to in vitro dissolution testing. The moisture had a significant impact on the amount dissolved for the solid dispersions. Molecular docking studies established that hydrogen bonding was critical for the stabilization of the solid dispersions. The rank order of the binding energy of the drug-polymer association was Soluplus (-6.21 kcal/mol)>HPMC-E5 (-3.21 kcal/mol)>PVP-K30 (-2.31 kcal/mol). PVP-K30 had the highest water uptake among the polymers, as did ASD system of lacidipine-PVP-K30 ASDs. In the Soluplus ASDs, with its strong drug-polymer interactions and low water uptake, moisture-induced solid-state crystallization was not observed. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Dispersion Models to Forecast Traffic-related Emissions in Urban Areas

    Directory of Open Access Journals (Sweden)

    Davide Scannapieco

    2011-11-01

    Full Text Available Down the centuries, a direct link had been developed between increase in mobility and increase in wealth. On the other hand, air emission of greenhouse gases (GHG due to vehicles equipped with internal combustion engines can be regarded as a negative pressure over the environment. In the coming decades, road transport is likely to remain a significant contributor to air pollution in cities. Many urban trips cover distances of less than 6 km. Since the effectiveness of catalytic converters in the initial minutes of engine operation is small, the average emission per distance driven is very high in urban areas. Also, poorly maintained vehicles that lack exhaust aftertreatment systems are responsible for a major part of pollutant emissions. Therefore in urban areas, where higher concentrations of vehicles can be easily found, air pollution represents a critical issue, being it related with both environment and human health protection: in truth, research in recent decades consistently indicates the adverse effects of outdoor air pollution on human health, and the evidence points to air pollution stemming from transport as an important contributor to these effects. Several institutions (EEA, USEPA, etc. focused their interest in dispersion models because of their potential effectiveness to forecast atmospheric pollution. Furthermore, air micropollutants such as Polycyclic Aromatic Compounds (PAH and Metallic Trace Elements (MTE are traffic-related and although very low concentrations their dispersion is a serious issue. However, dispersion models are usefully implemented to better manage this estimation problem. Nonetheless, policy makers and land managers have to deal with model selection, taking into account that several dispersion models are available, each one of them focused on specific goals (e.g., wind transport of pollutants, land morphology implementation, evaluation of micropollutants transport, etc.; a further aspect to be considered is

  9. Crystals in crystals

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Schmidt, I.; Carlsson, A.

    2005-01-01

    A major factor governing the performance of catalytically active particles supported on a zeolite carrier is the degree of dispersion. It is shown that the introduction of noncrystallographic mesopores into zeolite single crystals (silicalite-1, ZSM-5) may increase the degree of particle dispersion...... of the zeolite particles, particularly after thermal treatment. When using mesoporous zeolites, the particles were evenly distributed throughout the mesopore system of the zeolitic support, even after calcination, leading to nanocrystals within mesoporous zeolite single crystals....

  10. Gyro-viscosity and linear dispersion relations in pair-ion magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Kono, M. [Faculty of Policy Studies, Chuo University, Tokyo 192-0393 (Japan); Vranjes, J. [Instituto de Astrofisica de Canarias, Tenerife E38205 (Spain); Departamento de Astrofisica, Universidad de La Laguna, Tenerife E38205 (Spain)

    2015-11-15

    A fluid theory has been developed by taking account of gyro-viscosity to study wave propagation characteristics in a homogeneous pair-ion magnetized plasma with a cylindrical symmetry. The exact dispersion relations derived by the Hankel-Fourier transformation are shown comparable with those observed in the experiment by Oohara and co-workers. The gyro-viscosity is responsible for the change in propagation characteristics of the ion cyclotron wave from forward to backward by suppressing the effect of the thermal pressure which normally causes the forward nature of dispersion. Although the experiment has been already explained by a kinetic theory by the present authors, the kinetic derivations are so involved because of exact particle orbits in phase space, finite Lamor radius effects, and higher order ion cyclotron resonances. The present fluid theory provides a simple and transparent structure to the dispersion relations since the gyro-viscosity is renormalized into the ion cyclotron frequency which itself indicates the backward nature of dispersion. The usual disadvantage of a fluid theory, which treats only fundamental modes of eigen-waves excited in a system and is not able to describe higher harmonics that a kinetic theory does, is compensated by simple derivations and clear picture based on the renormalization of the gyro-viscosity.

  11. Study of Phonon Dispersion Relations in Cuprous Oxide by Inelastic Neutron Scattering

    DEFF Research Database (Denmark)

    Beg, M. M.; Shapiro, S. M.

    1976-01-01

    Phonon dispersion relations in Cu2O have been studied at 20°C using inelastic neutron scattering. Seven acoustic branches and twelve optical branches have been studied in detail in the three symmetry directions [00ζ], [ζζ0], and [ζζζ] of the cubic lattice. Four of the six zone-center phonons have...... been observed and the assignments and energies are confirmed as Γ25=87±2 cm-1, Γ12′=105±3 cm-1, Γ15=146±1 cm-1, and Γ2′≈347 cm-1. The dispersion relations agree only qualitatively with the rigid-ion-model calculations. It is suggested that more detailed calculations may be performed in the light...

  12. Spin-wave dispersion relations in disordered Fe-V alloys

    International Nuclear Information System (INIS)

    Nakai, Y.; Schibuya, N.; Kunitomi, N.; Wakabayashi, N.; Cooke, J.F.

    1982-01-01

    The spin-wave dispersion relations of the ferromagnetic disordered alloys Fe/sub 1-x/V/sub x/(x = 0.076, 0.135, 0.160, and 0.187) were studied by means of the inelastic scattering of neutrons. The observed dispersion relations are adequately represented by the power law, E = Dq 2 (1-βq 2 ), in a wide energy range up to 80 meV. The concentration dependence of the exchange stiffness constant D shows good agreement with previous results obtained by means of the small-angle scattering of neutrons and by the analysis of the temperature dependence of the bulk magnetization. The observed results can be explained by the Heisenberg model and, to some extent, by the itinerant-electron model

  13. Rainbows without unicorns: metric structures in theories with modified dispersion relations

    Science.gov (United States)

    Lobo, Iarley P.; Loret, Niccoló; Nettel, Francisco

    2017-07-01

    Rainbow metrics are a widely used approach to the metric formalism for theories with modified dispersion relations. They have had a huge success in the quantum gravity phenomenology literature, since they allow one to introduce momentum-dependent space-time metrics into the description of systems with a modified dispersion relation. In this paper, we introduce the reader to some realizations of this general idea: the original rainbow metrics proposal, the momentum-space-inspired metric and a Finsler geometry approach. As the main result of this work we also present an alternative definition of a four-velocity dependent metric which allows one to handle the massless limit. This paper aims to highlight some of their properties and how to properly describe their relativistic realizations.

  14. Traits related to species persistence and dispersal explain changes in plant communities subjected to habitat loss

    DEFF Research Database (Denmark)

    Marini, Lorenzo; Bruun, Hans Henrik; Heikkinen, Risto

    2012-01-01

    -history traits and by recalculating standardized landscape measures from the original geographical data. We assessed the responses of plant species richness to habitat area, connectivity, plant life-history traits and their interactions using linear mixed models. Results We found that the negative effect......Aim Habitat fragmentation is a major driver of biodiversity loss but it is insufficiently known how much its effects vary among species with different life-history traits; especially in plant communities, the understanding of the role of traits related to species persistence and dispersal...... in determining dynamics of species communities in fragmented landscapes is still limited. The primary aim of this study was to test how plant traits related to persistence and dispersal and their interactions modify plant species vulnerability to decreasing habitat area and increasing isolation. Location Five...

  15. Rainbows without unicorns: metric structures in theories with modified dispersion relations

    International Nuclear Information System (INIS)

    Lobo, Iarley P.; Loret, Niccolo; Nettel, Francisco

    2017-01-01

    Rainbow metrics are a widely used approach to the metric formalism for theories with modified dispersion relations. They have had a huge success in the quantum gravity phenomenology literature, since they allow one to introduce momentum-dependent space-time metrics into the description of systems with a modified dispersion relation. In this paper, we introduce the reader to some realizations of this general idea: the original rainbow metrics proposal, the momentum-space-inspired metric and a Finsler geometry approach. As the main result of this work we also present an alternative definition of a four-velocity dependent metric which allows one to handle the massless limit. This paper aims to highlight some of their properties and how to properly describe their relativistic realizations. (orig.)

  16. Correction of Cardy–Verlinde formula for Fermions and Bosons with modified dispersion relation

    Energy Technology Data Exchange (ETDEWEB)

    Sadatian, S. Davood, E-mail: sd-sadatian@um.ac.ir; Dareyni, H.

    2017-05-15

    Cardy–Verlinde formula links the entropy of conformal symmetry field to the total energy and its Casimir energy in a D-dimensional space. To correct black hole thermodynamics, modified dispersion relation can be used which is proposed as a general feature of quantum gravity approaches. In this paper, the thermodynamics of Schwarzschild four-dimensional black hole is corrected using the modified dispersion relation for Fermions and Bosons. Finally, using modified thermodynamics of Schwarzschild four-dimensional black hole, generalization for Cardy–Verlinde formula is obtained. - Highlights: • The modified Cardy–Verlinde formula obtained using MDR for Fermions and Bosons. • The modified entropy of the black hole used to correct the Cardy–Verlinde formula. • The modified entropy of the CFT has been obtained.

  17. Rainbows without unicorns: metric structures in theories with modified dispersion relations

    Energy Technology Data Exchange (ETDEWEB)

    Lobo, Iarley P. [Universita ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); ICRANet, Pescara (Italy); CAPES Foundation, Ministry of Education of Brazil, Brasilia (Brazil); Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, PB (Brazil); INFN Sezione Roma 1 (Italy); Loret, Niccolo [Ruder Boskovic Institute, Division of Theoretical Physics, Zagreb (Croatia); Nettel, Francisco [Universita ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Mexico (Mexico); INFN Sezione Roma 1 (Italy)

    2017-07-15

    Rainbow metrics are a widely used approach to the metric formalism for theories with modified dispersion relations. They have had a huge success in the quantum gravity phenomenology literature, since they allow one to introduce momentum-dependent space-time metrics into the description of systems with a modified dispersion relation. In this paper, we introduce the reader to some realizations of this general idea: the original rainbow metrics proposal, the momentum-space-inspired metric and a Finsler geometry approach. As the main result of this work we also present an alternative definition of a four-velocity dependent metric which allows one to handle the massless limit. This paper aims to highlight some of their properties and how to properly describe their relativistic realizations. (orig.)

  18. Spatial Statistics of Deep-Water Ambient Noise; Dispersion Relations for Sound Waves and Shear Waves

    Science.gov (United States)

    2015-09-30

    Dispersion Relations for Sound Waves and Shear Waves Michael J. Buckingham Marine Physical Laboratory , Scripps Institution of Oceanography University...dry, were all from laboratory experiments, since no in situ broadband shear-wave data were available at the time. (Since then, Megan Ballard and...Texas, 11 March 2014. 5. My graduate student, Simon Freeman, won Outstanding Student Paper Award for “Array-based hydroacoustic characterization of P, S

  19. $K^{\\pm}n$ forward dispersion relations and the KN$\\Sigma$ coupling constant

    CERN Document Server

    Baillon, Paul; Ferro-Luzzi, M; Jenni, Peter; Perreau, J M; Tripp, R D; Ypsilantis, Thomas; Déclais, Y; Séguinot, Jacques

    1976-01-01

    Recent measurements of the K/sup -/n forward scattering amplitude at 1.2, 1.4, 2.6 GeV/c are used in a once-subtracted dispersion relation to determine the value of the KN Sigma coupling constant. The result is g/sub Sigma //sup 2/=1.9+or-3.2, in agreement with the prediction of the SU(3) theory.

  20. Dispersion relation approach to sub-barrier heavy ion fusion reactions

    International Nuclear Information System (INIS)

    Franzin, V.L.M.; Hussein, M.S.

    1986-07-01

    With the aid of an inverse dispersion relation, which gives the imaginary part of the fusion inclusive polarization potential (IPP) in terms of the principal part integral involving the real part of the IPP, the sub-barrier fusion of heavy ions is discussed. The system 16 O+ A Sm is taken as an example. The reactive content of the extracted IPP is analysed within the coupled channels theory. (Author) [pt

  1. The dispersion relation for the forward elastic electron-atom scattering amplitude

    International Nuclear Information System (INIS)

    Amusia, M.Y.

    1978-01-01

    The analytical properties of forward elastic electron-atom scattering amplitude are discussed. It is noted that the occurrence of exchange between the incoming and atomic electrons leads to the appearance of a number of singularities on the negative real axis in the complex energy plane. The conclusion is drawn that the dispersion relation for the forward electron-atom scattering amplitude should also include an integration over the negative energy from - I to - infinity, where I is the ionization potential. (author)

  2. Pierce-type dispersion relation for an intense relativistic electron beam interacting with a slow-wave structure

    International Nuclear Information System (INIS)

    Chen, C.

    1994-01-01

    A Pierce-type dispersion relation is derived for the interaction of an intense relativistic electron beam with a cylindrical slow-wave structure of arbitrary corrugation depth. It is shown that near a resonance, the Pierce parameter can be expressed in terms of the vacuum dispersion function and the beam current. The dispersion relation is valid in both the low-current (Compton) regime and the high-current (Raman) regime. The dispersion characteristics of the interaction, such as the linear instability growth rate and bandwidth, are analyzed for both regimes

  3. Black hole radiation with modified dispersion relation in tunneling paradigm: Static frame

    Directory of Open Access Journals (Sweden)

    Jun Tao

    2017-09-01

    Full Text Available To study possible deviations from the Hawking's prediction, we assume that the dispersion relations of matter fields are modified at high energies and use the Hamilton–Jacobi method to investigate the corresponding effects on the Hawking radiation in this paper. The preferred frame is the static frame of the black hole. The dispersion relation adopted agrees with the relativistic one at low energies but is modified near the Planck mass mp. We calculate the corrections to the Hawking temperature for massive and charged particles to O(mp−2 and massless and neutral particles to all orders. Our results suggest that the thermal spectrum of radiations near horizon is robust, e.g. corrections to the Hawking temperature are suppressed by mp. After the spectrum of radiations near the horizon is obtained, we use the brick wall model to compute the thermal entropy of a massless scalar field near the horizon of a 4D spherically symmetric black hole. We find that the subleading logarithmic term of the entropy does not depend on how the dispersion relations of matter fields are modified. Finally, the luminosities of black holes are computed by using the geometric optics approximation.

  4. The role of environment, dispersal and competition in explaining reduced co-occurrence among related species.

    Directory of Open Access Journals (Sweden)

    Ben G Weinstein

    Full Text Available The composition of ecological assemblages depends on a variety of factors including environmental filtering, biotic interactions and dispersal limitation. By evaluating the phylogenetic pattern of assemblages, we gain insight into the relative contribution of these mechanisms to generating observed assemblages. We address some limitations in the field of community phylogenetics by using simulations, biologically relevant null models, and cost distance analysis to evaluate simultaneous mechanisms leading to observed patterns of co-occurrence. Building from past studies of phylogenetic community structure, we applied our approach to hummingbird assemblages in the Northern Andes. We compared the relationship between relatedness and co-occurrence among predicted assemblages, based on estimates of suitable habitat and dispersal limitation, and observed assemblages. Hummingbird co-occurrence peaked at intermediate relatedness and decreased when a closely-related species was present. This result was most similar to simulations that included simultaneous effects of phylogenetic conservatism and repulsion. In addition, we found older sister taxa were only weakly more separated by geographic barriers, suggesting that time since dispersal is unlikely to be the sole factor influencing co-occurrence of closely related species. Our analysis highlights the role of multiple mechanisms acting simultaneously, and provides a hypothesis for the potential importance of competition at regional scales.

  5. crystal

    Science.gov (United States)

    Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

    2014-07-01

    A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

  6. Simultaneous determination of ordinary and extraordinary refractive index dispersions of nematic liquid crystals in the visible and near-infrared regions from an interference spectrum

    Science.gov (United States)

    Ozaki, Ryotaro; Nishi, Koji; Kan, Takayuki; Kadowaki, Kazunori

    2016-10-01

    An improved interference method is proposed to determine ordinary and extraordinary refractive index dispersions of nematic liquid crystals (LCs). In this method, an LC cell coated with a thin metal layer is used as a Fabry-Perot interferometer, which shows us a sharp transmission fringe. To ensure high reliability, the wavelength dispersion of the refractive index of the metal is taken into account in fitting calculation. In spite of measuring ordinary and extraordinary components, the LC cell, polarizers, and other equipment are not rotated during the experiment. The index evaluation from a single spectrum avoids errors depending on the measurement position owing to non-uniformities of molecular orientation and cell thickness because we can obtain the two indices at exactly the same position. This system can adapt to a wide frequency range and does not require any specific wavelength light source or laser. We demonstrate the determination of ordinary and extraordinary refractive index dispersions of a nematic liquid crystal in the visible and near-infrared regions. Furthermore, we quantitatively reproduce the measured spectrum by calculation using the measured refractive indices.

  7. Fiber optical parametric oscillator based on photonic crystal fiber pumped with all-normal-dispersion mode-locked Yb:fiber laser

    International Nuclear Information System (INIS)

    Gou Dou-Dou; Yang Si-Gang; Zhang Lei; Wang Xiao-Jian; Chen Hong-Wei; Chen Ming-Hua; Xie Shi-Zhong; Chen Wei; Luo Wen-Yong

    2014-01-01

    We demonstrate a cost effective, linearly tunable fiber optical parametric oscillator based on a home-made photonic crystal fiber pumped with a mode-locked ytterbium-doped fiber laser, providing linely tuning ranges from 1018 nm to 1038 nm for the idler wavelength and from 1097 nm to 1117 nm for the signal wavelength by tuning the pump wavelength and the cavity length. In order to obtain the desired fiber with a zero dispersion wavelength around 1060 nm, eight samples of photonic crystal fibers with gradually changed structural parameters are fabricated for the reason that it is difficult to accurately customize the structural dimensions during fabrication. We verify the usability of the fabricated fiber experimentally via optical parametric generation and conclude a successful procedure of design, fabirication, and verification. A seed source of home-made all-normal-dispersion mode-locked ytterbium-doped fiber laser with 38.57 ps pulsewidth around the 1064 nm wavelength is used to pump the fiber optical parametric oscillator. The wide picosecond pulse pump laser enables a larger walk-off tolerance between the pump light and the oscillating light as well as a longer photonic crystal fiber of 20 m superior to the femtosecond pulse lasers, resulting in a larger parametric amplification and a lower threshold pump power of 15.8 dBm of the fiber optical parametric oscillator. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  8. Natural age dispersion arising from the analysis of broken crystals. Part I: Theoretical basis and implications for the apatite (U-Th)/He thermochronometer

    Science.gov (United States)

    Brown, Roderick W.; Beucher, Romain; Roper, Steven; Persano, Cristina; Stuart, Fin; Fitzgerald, Paul

    2013-12-01

    Over the last decade major progress has been made in developing both the theoretical and practical aspects of apatite (U-Th)/He thermochronometry and it is now standard practice, and generally seen as best practice, to analyse single grain aliquots. These individual prismatic crystals are often broken and are fragments of larger crystals that have broken during mineral separation along the weak basal cleavage in apatite. This is clearly indicated by the common occurrence of only 1 or no clear crystal terminations present on separated apatite grains, and evidence of freshly broken ends when grains are viewed using a scanning electron microscope. This matters because if the 4He distribution within the whole grain is not homogeneous, because of partial loss due to thermal diffusion for example, then the fragments will all yield ages different from each other and from the whole grain age. Here we use a numerical model with a finite cylinder geometry to approximate 4He ingrowth and thermal diffusion within hexagonal prismatic apatite crystals. This is used to quantify the amount and patterns of inherent, natural age dispersion that arises from analysing broken crystals. A series of systematic numerical experiments were conducted to explore and quantify the pattern and behaviour of this source of dispersion using a set of 5 simple thermal histories that represent a range of plausible geological scenarios. In addition some more complex numerical experiments were run to investigate the pattern and behaviour of grain dispersion seen in several real data sets. The results indicate that natural dispersion of a set of single fragment ages (defined as the range divided by the mean) arising from fragmentation alone varies from c. 7% even for rapid (c. 10 °C/Ma), monotonic cooling to over 50% for protracted, complex histories that cause significant diffusional loss of 4He. The magnitude of dispersion arising from fragmentation scales with the grain cylindrical radius, and is of

  9. Acoustic modes of the phonon dispersion relation of NbD/sub x/ alloys

    International Nuclear Information System (INIS)

    Rowe, J.M.; Vagelatos, N.; Rush, J.J.; Flotow, H.E.

    1975-01-01

    The acoustic modes of the phonon dispersion relation in Nb, NbD 0 . 15 , and NbD 0 . 45 were measured at 473 0 K for phonons with wave vectors along the [100], [110], and [111] axes by coherent neutron scattering. The observed neutron groups for both alloys were well defined, with little or no apparent broadening. Results are compared to similar data for Nb--Mo alloys and with previous lattice-dynamics results for PdD 0 . 63 . This comparison shows that despite differences in detail, the general features of the dispersion relations of NbD/sub x/ and Nb--Mo are similar after allowing for the differences in lattice parameters for the two alloys. The measured dispersion curves and derived phonon frequency distributions for the Nb--D alloys are quite different from the analogous results for PdD 0 . 63 in that the average acoustic phonon frequencies increase with increasing deuterium concentration and lattice parameter

  10. Magnon dispersion relation and exchange interactions in MnF2

    DEFF Research Database (Denmark)

    Nikotin, O.; Lindgård, Per-Anker; Dietrich, O. W.

    1969-01-01

    The magnon dispersion relation for MnF2 at 4·2 °K has been measured by means of the triple-axis neutron scattering technique along the symmetry lines in the (010) plane of the Brillouin zone. Using an exact dipole model, the three nearest-neighbour exchange constants were found to be J1 = 0·028 ± 0......·001 mev, J2 = -0·152 ± 0·001 mev and J3 = -0·004 ± 0·001 mev. The second moment was also calculated with this model. The density of magnon states was evaluated by applying a six-parameter simulation of the dispersion surface. The critical points in the density of states agree well with those obtained...

  11. EXPERIMENTAL DETERMINATION OF WHISTLER WAVE DISPERSION RELATION IN THE SOLAR WIND

    Energy Technology Data Exchange (ETDEWEB)

    Stansby, D.; Horbury, T. S.; Chen, C. H. K.; Matteini, L., E-mail: david.stansby14@imperial.ac.uk [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)

    2016-09-20

    The origins and properties of large-amplitude whistler wavepackets in the solar wind are still unclear. In this Letter, we utilize single spacecraft electric and magnetic field waveform measurements from the ARTEMIS mission to calculate the plasma frame frequency and wavevector of individual wavepackets over multiple intervals. This allows direct comparison of experimental measurements with theoretical dispersion relations to identify the observed waves as whistler waves. The whistlers are right-hand circularly polarized, travel anti-sunward, and are aligned with the background magnetic field. Their dispersion is strongly affected by the local electron parallel beta in agreement with linear theory. The properties measured are consistent with the electron heat flux instability acting in the solar wind to generate these waves.

  12. Nearest-neighbour-interaction model in the coupled-optical-phonon-mode theory of the infrared dispersion in monoclinic crystals: Application to Tutton salt single crystal.

    Science.gov (United States)

    Ivanovski, V; Ivanovski, G

    2010-05-01

    The coupled-optical-phonon-mode theory of Barker and Hopfield of two mode interaction in isotropic crystals has been extended to monoclinic crystals. The analytical expressions for the calculation of the dielectric tensor elements in the ac crystal plane have been derived. It has been shown that the interaction dielectric model is a generalized expression of the dielectric tensor for monoclinic case when no interaction between modes is present. Also, the results of Barker and Hopfield are obtained from this more general theory, when an isotropic case is considered. In order to be able to investigate real crystals, meaning extending the interactions to a large number of pairs of modes, but at the same time to make the fitting procedure possible, a model dielectric function taking into account the interaction between modes with closest frequencies has been derived. The validity of the model obtained has been tested on a Tutton salt single crystal of K(2)Co(SO(4))(2).6H(2)O. The recorded spectra from the ac crystal plane were fitted in order to obtain best fit parameters. The comparison between the experimentally recorded spectra and the model reflectance function give good results and verify this model to be applicable. Copyright 2010 Elsevier B.V. All rights reserved.

  13. Numerical investigation of zeros of some dispersion relations appearing in sound attenuation problems in a circular lined duct

    Directory of Open Access Journals (Sweden)

    Loredana TANASIE

    2012-12-01

    Full Text Available In this paper the zeros of some dispersion relations apperaring in sound attenuation problems in circular lined ducts, carrying a gas flow, are investigated numerically. To find the values of frequencies for which the dispersion relations vanish is not easy at all. That is beacause these relations contain the solution of an initial value problem which depends on the unknown frequency and can not be found explicitly. In order to overcome this difficulty we consider approximate dispersion relations, obtained by replacing in the shear flow the solution of the initial value problem by its Taylor’s polynomial approximate. For numerical computations typical aeronautical examples are considered.

  14. Diffusion related isotopic fractionation effects with one-dimensional advective–dispersive transport

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Bruce S. [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada); Lollar, Barbara Sherwood [Earth Sciences Department, University of Toronto, 22 Russell Street, Toronto, ON M5S 3B1 (Canada); Passeport, Elodie [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada); Chemical Engineering and Applied Chemistry Department, University of Toronto, 200 College Street, Toronto, ON M5S 3E5 (Canada); Sleep, Brent E., E-mail: sleep@ecf.utoronto.ca [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada)

    2016-04-15

    Aqueous phase diffusion-related isotope fractionation (DRIF) for carbon isotopes was investigated for common groundwater contaminants in systems in which transport could be considered to be one-dimensional. This paper focuses not only on theoretically observable DRIF effects in these systems but introduces the important concept of constraining “observable” DRIF based on constraints imposed by the scale of measurements in the field, and on standard limits of detection and analytical uncertainty. Specifically, constraints for the detection of DRIF were determined in terms of the diffusive fractionation factor, the initial concentration of contaminants (C{sub 0}), the method detection limit (MDL) for isotopic analysis, the transport time, and the ratio of the longitudinal mechanical dispersion coefficient to effective molecular diffusion coefficient (D{sub mech}/D{sub eff}). The results allow a determination of field conditions under which DRIF may be an important factor in the use of stable carbon isotope measurements for evaluation of contaminant transport and transformation for one-dimensional advective–dispersive transport. This study demonstrates that for diffusion-dominated transport of BTEX, MTBE, and chlorinated ethenes, DRIF effects are only detectable for the smaller molar mass compounds such as vinyl chloride for C{sub 0}/MDL ratios of 50 or higher. Much larger C{sub 0}/MDL ratios, corresponding to higher source concentrations or lower detection limits, are necessary for DRIF to be detectable for the higher molar mass compounds. The distance over which DRIF is observable for VC is small (less than 1 m) for a relatively young diffusive plume (< 100 years), and DRIF will not easily be detected by using the conventional sampling approach with “typical” well spacing (at least several meters). With contaminant transport by advection, mechanical dispersion, and molecular diffusion this study suggests that in field sites where D{sub mech}/D{sub eff} is

  15. Phylogenetic patterns in zopherine beetles are related to ecological niche width and dispersal limitation.

    Science.gov (United States)

    Baselga, Andrés; Recuero, Ernesto; Parra-Olea, Gabriela; García-París, Mario

    2011-12-01

    Niche conservatism has been proposed as the mechanism driving speciation in temperate montane clades through range fragmentation during climatic oscillations. Thus, a negative relationship between speciation rates and niche width is expected. Here, we test this prediction using American zopherine beetles. Our phylogenetic analyses recovered two clades in addition to that of the genus Zopherus: the genera Verodes and Phloeodes, which originated most likely in the Eocene, and diversified during the Miocene and the Pliocene. The assessment of clade niche width in relation to clade diversity supported the proposition of narrow niches leading to a higher probability of range fragmentation during climatic oscillations, thus increasing speciation. Additionally, almost all current populations of Phloeodes and Verodes are located within regions that retained favourable climatic conditions across warm and cold Pleistocene periods, suggesting that dispersal limitation is a strong factor controlling clade distribution. In sum, our results suggest that (i) niche width is a major determinant of the probability of speciation in temperate montane clades, by controlling the probability of potential range fragmentation and (ii) dispersal limitation is also a major determinant of the speciation process, by increasing the fragmentation of realized ranges even when potential distributions are cyclically fused during climatic oscillations. When dispersal limitation is extreme, as in zopherine beetles, populations persist just in those areas that have retained suitable conditions during extremes of past climatic oscillations. Paradoxically, this relict condition confers zopherine beetles great resilience for facing future climate change. © 2011 Blackwell Publishing Ltd.

  16. Enthalpy relaxation studies of two structurally related amorphous drugs and their binary dispersions.

    Science.gov (United States)

    Bansal, Shyam Sunder; Kaushal, Aditya Mohan; Bansal, Arvind Kumar

    2010-11-01

    The purpose of the current study was to evaluate the enthalpy relaxation behavior of valdecoxib (VLB) and etoricoxib (ETB) and their binary dispersions to derive relaxation constants and to understand their molecular mobilities. Solid dispersions of VLB and ETB were prepared with 1%, 2%, 5%, 10%, 15%, and 20% (w/w) concentrations of polyvinylpyrrolidone (PVP) in situ using differential scanning calorimetry (DSC). Enthalpy relaxation studies were carried out with isothermal storage periods of 1, 2, 4, 6, 16, and 24 hours at 40°C and 0% relative humidity (RH). PVP increased the glass transition temperature (T(g)) and decreased the enthalpy relaxation. Significant differences between two drugs were observed with respect to their relaxation behavior which may be due to differences in intermolecular interactions as predicted by Couchman-Karasz equation and molecular mobility. Kohlrausch-Williams-Watts equation was found to be inadequate in describing complex molecular relaxations in binary dispersions. The enthalpy relaxation behavior of VLB and ETB was found to be significantly different. PVP stabilized VLB significantly; however, its effect on ETB was negligible. The extent of enthalpy relaxation was found to correlate with hydrogen bonding tendency of the drug molecules. The outcome can help in rational designing of amorphous systems with optimal performance.

  17. Relative dispersion of clustered drifters in a small micro-tidal estuary

    Science.gov (United States)

    Suara, Kabir; Chanson, Hubert; Borgas, Michael; Brown, Richard J.

    2017-07-01

    Small tide-dominated estuaries are affected by large scale flow structures which combine with the underlying bed generated smaller scale turbulence to significantly increase the magnitude of horizontal diffusivity. Field estimates of horizontal diffusivity and its associated scales are however rare due to limitations in instrumentation. Data from multiple deployments of low and high resolution clusters of GPS-drifters are used to examine the dynamics of a surface flow in a small micro-tidal estuary through relative dispersion analyses. During the field study, cluster diffusivity, which combines both large- and small-scale processes ranged between, 0.01 and 3.01 m2/s for spreading clusters and, -0.06 and -4.2 m2/s for contracting clusters. Pair-particle dispersion, Dp2, was scale dependent and grew as Dp2 ∼ t1.83 in streamwise and Dp2 ∼ t0.8 in cross-stream directions. At small separation scale, pair-particle (d law and became weaker as separation scale increases. Pair-particle diffusivity was described as Kp ∼ d1.01 and Kp ∼ d0.85 in the streamwise and cross-stream directions, respectively for separation scales ranging from 0.1 to 10 m. Two methods were used to identify the mechanism responsible for dispersion within the channel. The results clearly revealed the importance of strain fields (stretching and shearing) in the spreading of particles within a small micro-tidal channel. The work provided input for modelling dispersion of passive particle in shallow micro-tidal estuaries where these were not previously experimentally studied.

  18. Crystal structure determination of solar cell materials: Cu2ZnSnS4 thin films using X-ray anomalous dispersion

    International Nuclear Information System (INIS)

    Nozaki, Hiroshi; Fukano, Tatsuo; Ohta, Shingo; Seno, Yoshiki; Katagiri, Hironori; Jimbo, Kazuo

    2012-01-01

    Highlights: ► Cu 2 ZnSnS 4 thin films as a solar cell material were synthesized. ► The wavelength dependences of the diffraction intensity were measured. ► The crystal structures were clearly identified as kesterite structure for all samples. ► Crystal structure analysis revealed that the atomic compositions were Cu/(Zn + Sn) = 0.97 and Zn/Sn = 1.42 for the sample synthesized using stoichiometric amount of starting materials. - Abstract: The crystal structure of Cu 2 ZnSnS 4 (CZTS) thin films fabricated by vapor-phase sulfurization was determined using X-ray anomalous dispersion. High statistic synchrotron radiation X-ray diffraction data were collected from very small amounts of powder. By analyzing the wavelength dependencies of the diffraction peak intensities, the crystal structure was clearly identified as kesterite. Rietveld analysis revealed that the atomic composition deviated from stoichiometric composition, and the compositions were Cu/(Zn + Sn) = 0.97, and Zn/Sn = 1.42.

  19. Wave-dispersive x-ray spectrometer for simultaneous acquisition of several characteristic lines based on strongly and accurately shaped Ge crystal

    International Nuclear Information System (INIS)

    Hayashi, Kouichi; Nakajima, Kazuo; Fujiwara, Kozo; Nishikata, Susumu

    2008-01-01

    Si and Ge are widely used as analyzing crystals for x-rays. Drastic and accurate shaping of Si or Ge gives significant advance in the x-ray field, although covalently bonded Si or Ge crystals have long been believed to be not deformable to various shapes. Recently, we developed a deformation technique for obtaining strongly and accurately shaped Si or Ge wafers of high crystal quality, and the use of the deformed wafer made it possible to produce fine-focused x-rays. In the present study, we prepared a cylindrical Ge wafer with a radius of curvature of 50 mm, and acquired fluorescent x-rays simultaneously from four elements by combining the cylindrical Ge wafer with a position-sensitive detector. The energy resolution of the x-ray fluorescence spectrum was as good as that obtained using a flat single crystal, and its gain was over 100. The demonstration of the simultaneous acquisition of high-resolution x-ray fluorescence spectra indicated various possibilities of x-ray spectrometry, such as one-shot x-ray spectroscopy and highly efficient wave-dispersive x-ray spectrometers

  20. Nano crystals-Related Synthesis, Assembly, and Energy Applications

    International Nuclear Information System (INIS)

    Dai, Q.; Hu, M.Z.; Yu, B.Z.; William, W.; Seo, J.

    2011-01-01

    Fundamental material properties have been dramatically altered in the nano scale regime because of quantum confinement effect. The unique size-tunable functionalities of nano materials make them involved in an extensive variety of energy applications, such as light-emitting diodes and solar cells. These applications have been demonstrated to cut energy consumption. In response to the ever-growing energy demands as well as the concerns of global warming, researchers are actively placing their enormous emphasis on the exploration of energy savings. During this exploration, the primary stage requires the design of appropriate strategies for the synthesis of high-quality nano crystals in terms of size uniformity and superior optical/electronic properties. Especially, there is a need to seek green-chemistry approaches for the synthesis of environmentally benign and user-friendly nano crystals. Another recent area of focus is the use of individual nano crystals as building blocks for self-assembly, providing new opportunities to improve the nano crystal performance

  1. Does dispersal ability affect the relative importance of environmental control and spatial structuring of littoral macroinvertebrate communities?

    Science.gov (United States)

    Heino, Jani

    2013-04-01

    Both spatial processes and environmental control may structure metacommunities, but their relative importance may be contingent on the dispersal ability of organisms. I examined the roles of spatial and environmental factors for the structuring of littoral macroinvertebrate communities across a set of lakes in a boreal drainage basin. I hypothesized that dispersal ability would affect the relative importance of spatial processes and environmental control, and thus the biological data were divided into four groups of species differing in dispersal ability. In general, the group of the strongest aerial dispersers showed greatest relative pure environmental control and least pure spatial structuring of community structure and species richness, while spatial processes seemed to be more important for the other three dispersal ability groups. However, these results were contingent on the indirect measure of spatial processes, with the spatial variables and connectivity variables providing slightly different insights into the spatial processes and environmental control of metacommunity structuring. It appears, however, that dispersal ability has effects on the spatial processes and environmental control important in metacommunity organization, with strong dispersers being more under environmental control and less affected by spatial processes compared to weak dispersers.

  2. Bounds on Cubic Lorentz-Violating Terms in the Fermionic Dispersion Relation

    OpenAIRE

    Bertolami, O.; Rosa, J. G.

    2004-01-01

    We study the recently proposed Lorentz-violating dispersion relation for fermions and show that it leads to two distinct cubic operators in the momentum. We compute the leading order terms that modify the non-relativistic equations of motion and use experimental results for the hyperfine transition in the ground state of the ${}^9\\textrm Be^+$ ion to bound the values of the Lorentz-violating parameters $\\eta_1$ and $\\eta_2$ for neutrons. The resulting bounds depend on the value of the Lorenz-...

  3. Backwards and forwards relative dispersion in turbulent flow: An experimental investigation

    DEFF Research Database (Denmark)

    Berg, J.; Lüthi, B.; Mann, J.

    2006-01-01

    From particle tracking velocimetry we present an experimental measure of the ratio between backwards and forwards relative dispersion in an intermediate Reynolds number turbulent flow. Lack of time-reversal symmetry implies that their ratio may be different from 1. From a stochastic model, this has...... recently been studied by Sawford [Phys. Fluids 17, 095109 (2005)] giving ratios between 5 and 20. We find a value of approximately 2 and discuss it in the context of the characteristics of the rate of strain tensor s(ij). An analysis of a direct numerical simulation by Biferale [Phys. Rev. Lett. 93, 064502...

  4. Design optimization of a compact photonic crystal microcavity based on slow light and dispersion engineering for the miniaturization of integrated mode-locked lasers

    Directory of Open Access Journals (Sweden)

    Malik Kemiche

    2018-01-01

    Full Text Available We exploit slow light (high ng modes in planar photonic crystals in order to design a compact cavity, which provides an attractive path towards the miniaturization of near-infrared integrated fast pulsed lasers. By applying dispersion engineering techniques, we can design structures with a low dispersion, as needed by mode-locking operation. Our basic InP SiO2 heterostructure is robust and well suited to integrated laser applications. We show that an optimized 30 μm long cavity design yields 9 frequency-equidistant modes with a FSR of 178 GHz within a 11.5 nm bandwidth, which could potentially sustain the generation of optical pulses shorter than 700 fs. In addition, the numerically calculated quality factors of these modes are all above 10,000, making them suitable for reaching laser operation. Thanks to the use of a high group index (28, this cavity design is almost one order of magnitude shorter than standard rib-waveguide based mode-locked lasers. The use of slow light modes in planar photonic crystal based cavities thus relaxes the usual constraints that tightly link the device size and the quality (peak power, repetition rate of the pulsed laser signal.

  5. Dispersion relations of density fluctuations observed by heavy ion beam probe in the TEXT tokamak

    International Nuclear Information System (INIS)

    Ross, D.W.

    1990-09-01

    Wave numbers as functions of frequency for density fluctuations in the core of the TEXT tokamak are measured in Heavy Ion Beam Probe experiments by analyzing the relative phases of signals originating from nearby points in the plasma. The adjacent points are typically 2 cm apart, with their relative orientation (δr, δθ) depending on position (r,θ). for angular frequencies ω ≤ 10 6 /s the signals are quite coherent, leading to reasonably well-defined ''dispersion relations.'' These do not correspond to known modes of the drift wave type, i.e., ballooning or slab-like electron drift waves or ion temperature gradient modes. The effect of finite sample volume size does not significantly alter this conclusion. 25 refs., 6 figs., 3 tabs

  6. Three-dimensional free electron laser dispersion relation including betatron oscillations

    International Nuclear Information System (INIS)

    Chin, Y.H.; Kim, K.J.; Xie, M.

    1991-08-01

    We have developed a 3-D FEL theory based upon the Maxwell-Vlasov equations including the effects of the energy spread and emittance of the electron beam, and of betatron oscillations. The radiation field is expressed in terms of the Green's function of the inhomogeneous wave equation and the distribution function of the electron beam. The distribution function is expanded in terms of a set of orthogonal functions determined by the unperturbed particle distribution. The coupled Maxwell-Vlasov equations are then reduced to a matrix equation, from which a dispersion relation for the eigenvalues is derived. In the limit of small betatron oscillation frequency, the present dispersion relation reduces to the well-known cubic equation of the one-dimensional theory in the limit of large beam size, and it gives the correct gain in the limit of small beam size. Comparisons of our numerical results with other approaches show good agreement. We present a handy empirical formula for the FEL gain of a 3-D Gaussian beam, as a function of the scaled parameters, that can be used for a quick estimate of the grain. 5 refs., 2 figs

  7. Dispersion relations in the noncommutative φ3 and Wess-Zumino model in the Yang-Feldman formalism

    International Nuclear Information System (INIS)

    Doescher, C.; Zahn, J.

    2006-05-01

    We study dispersion relations in the noncommutative φ 3 and Wess-Zumino model in the Yang-Feldman formalism at one-loop order. Non-planar graphs lead to a distortion of the dispersion relation. We find that this effect is small if the scale of noncommutativity is identified with the Planck scale and parameters typical for a Higgs field are employed. (Orig.)

  8. The age-velocity dispersion relation of the Galactic discs from LAMOST-Gaia data

    Science.gov (United States)

    Yu, Jincheng; Liu, Chao

    2018-03-01

    We present the age-velocity dispersion relation (AVR) in three dimensions in the solar neighbourhood using 3564 commonly observed sub-giant/red giant branch stars selected from The Large Sky Area Multi-Object Fiber Spectroscopic Telescope, which gives the age and radial velocity, and Gaia, which measures the distance and proper motion. The stars are separated into metal-poor ([Fe/H] -0.2 dex) groups, so that the metal-rich stars are mostly α-poor, while the metal-poor group are mostly contributed by α-enhanced stars. Thus, the old and metal-poor stars likely belong to the chemically defined thick disc population, while the metal-rich sample is dominated by the thin disc. The AVR for the metal-poor sample shows an abrupt increase at ≳7 Gyr, which is contributed by the thick disc component. On the other hand, most of the thin disc stars with [Fe/H] > -0.2 dex display a power-law-like AVR with indices of about 0.3-0.4 and 0.5 for the in-plane and vertical dispersions, respectively. This is consistent with the scenario that the disc is gradually heated by the spiral arms and/or the giant molecular clouds. Moreover, the older thin disc stars (>7 Gyr) have a rounder velocity ellipsoid, i.e. σϕ/σz is close to 1.0, probably due to the more efficient heating in vertical direction. Particularly for the old metal-poor sample located with |z| > 270 pc, the vertical dispersion is even larger than its azimuthal counterpart. Finally, the vertex deviations and the tilt angles are plausibly around zero with large uncertainties.

  9. Quasiparticles of widely tuneable inertial mass: The dispersion relation of atomic Josephson vortices and related solitary waves

    Directory of Open Access Journals (Sweden)

    Sophie S. Shamailov, Joachim Brand

    2018-03-01

    Full Text Available Superconducting Josephson vortices have direct analogues in ultracold-atom physics as solitary-wave excitations of two-component superfluid Bose gases with linear coupling. Here we numerically extend the zero-velocity Josephson vortex solutions of the coupled Gross-Pitaevskii equations to non-zero velocities, thus obtaining the full dispersion relation. The inertial mass of the Josephson vortex obtained from the dispersion relation depends on the strength of linear coupling and has a simple pole divergence at a critical value where it changes sign while assuming large absolute values. Additional low-velocity quasiparticles with negative inertial mass emerge at finite momentum that are reminiscent of a dark soliton in one component with counter-flow in the other. In the limit of small linear coupling we compare the Josephson vortex solutions to sine-Gordon solitons and show that the correspondence between them is asymptotic, but significant differences appear at finite values of the coupling constant. Finally, for unequal and non-zero self- and cross-component nonlinearities, we find a new solitary-wave excitation branch. In its presence, both dark solitons and Josephson vortices are dynamically stable while the new excitations are unstable.

  10. Supersaturation, nucleation, and crystal growth during single- and biphasic dissolution of amorphous solid dispersions: polymer effects and implications for oral bioavailability enhancement of poorly water soluble drugs.

    Science.gov (United States)

    Sarode, Ashish L; Wang, Peng; Obara, Sakae; Worthen, David R

    2014-04-01

    The influence of polymers on the dissolution, supersaturation, crystallization, and partitioning of poorly water soluble compounds in biphasic media was evaluated. Amorphous solid dispersions (ASDs) containing felodipine (FLD) and itraconazole (ITZ) were prepared by hot melt mixing (HMM) using various polymers. The ASDs were analyzed using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and HPLC. Amorphous drug conversion was confirmed using DSC and PXRD, and drug stability by HPLC. Single- and biphasic dissolution studies of the ASDs with concurrent dynamic light scattering (DLS) and polarized light microscopic (PLM) analysis of precipitated drugs were performed. HPLC revealed no HMM-induced drug degradation. Maximum partitioning into the organic phase was dependent upon the degree of supersaturation. Although the highest supersaturation of FLD was attained using Eudragit® EPO and AQOAT® AS-LF with better nucleation and crystal growth inhibition using the latter, higher partitioning of the drug into the organic phase was achieved using Pharmacoat® 603 and Kollidon® VA-64 by maintaining supersaturation below critical nucleation. Critical supersaturation for ITZ was surpassed using all of the polymers, and partitioning was dependent upon nucleation and crystal growth inhibition in the order of Pharmacoat® 603>Eudragit® L-100-55>AQOAT® AS-LF. HMM drug-polymer systems that prevent drug nucleation by staying below critical supersaturation are more effective for partitioning than those that achieve the highest supersaturation. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Experimental studies of dispersive double reflections excited in cylindrically bent perfect-crystal slabs at a constant neutron wavelength

    Czech Academy of Sciences Publication Activity Database

    Mikula, Pavol; Vrána, Miroslav; Šaroun, Jan; Davydov, Vadim; Em, V.; Seong, B. S.

    2012-01-01

    Roč. 45, č. 1 (2012), s. 98-105 ISSN 0021-8898 R&D Projects: GA ČR GAP204/10/0654 Institutional research plan: CEZ:AV0Z10480505 Keywords : RESIDUAL STRAIN-STRESS INSTRUMENT * MULTIPLE BRAGG-REFLECTIONS * SINGLE-CRYSTAL Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.343, year: 2012

  12. Crystal Structure of Three Compounds Related to Triphenylene and Tetracyanoquinodimethane

    DEFF Research Database (Denmark)

    Andresen, T.L.; Krebs, Frederik C; Larsen, M.

    1999-01-01

    The crystal structures of a charge-transfer complex of triphenylene with 1,3,5-tris(2,2-dicyanovinyl) benzene (1), a complex of 2,3,6,7,10,11-hexamethoxytriphenylene with 2,5-dichlorotetracyanoquinodimethane (2) and also 2,5-dichlorotetracyanoquinodimethane itself (3) have been determined. Compou...... = 83.73(3), gamma = 66.06(3)degrees. Compound 3 is monoclinic, space group I2/a (C2/c), with a = 13.692(3), b = 7.7183(15), c = 16.391(3) Angstrom, beta = 99.47(3)degrees. The structures of 1 and 2 consist of mixed stacks of donors and accepters. The structures of 2 and 3 both include 1...

  13. Effects of weak nonlinearity on dispersion relations and frequency band-gaps of periodic structures

    DEFF Research Database (Denmark)

    Sorokin, Vladislav; Thomsen, Jon Juel

    2015-01-01

    The analysis of the behaviour of linear periodic structures can be traced back over 300 years, to Sir Isaac Newton, and still attracts much attention. An essential feature of periodic struc-tures is the presence of frequency band-gaps, i.e. frequency ranges in which waves cannot propagate....... Determination of band-gaps and the corresponding attenuation levels is an im-portant practical problem. Most existing analytical methods in the field are based on Floquet theory; e.g. this holds for the classical Hill’s method of infinite determinants, and the method of space-harmonics. However, application....... The present work deals with analytically predicting dynamic responses for nonlinear continuous elastic periodic structures. Specifically, the effects of weak nonlinearity on the dispersion re-lation and frequency band-gaps of a periodic Bernoulli-Euler beam performing bending os-cillations are analyzed...

  14. Expressions to Rayleigh circumferential phase velocity and dispersion relation for a cylindrical surface under mechanical pressure

    Science.gov (United States)

    Sebold, Jean Eduardo; de Lacerda, Luiz Alkimin

    2018-04-01

    This paper describes a substantiated mathematical theory for Rayleigh waves propagated on some types of metal cylinders. More specifically, it presents not only a new way to express the dispersion relation of Rayleigh waves propagated on the cylindrical surface, but also how it can be used to construct a mathematical equation showing that the applied static mechanical pressure affects the shear modulus of the metal cylinder. All steps, required to conclude the process, consider the equation of motion as a function of radial and circumferential coordinates only, while the axial component can be overlooked without causing any problems. Some numerical experiments are done to illustrate the changes in the Rayleigh circumferential phase velocity in a metal cylindrical section due to static mechanical pressure around its external surface.

  15. Highly dispersed spherical Bi3.25La0.75Ti3O12 nanocrystals via topotactic crystallization of aggregation-free gel particles from an effective inverse miniemulsion sol–gel approach

    International Nuclear Information System (INIS)

    Wang, Aijun; Zeng, Yanwei; Han, Longxiang; Ding, Chuan; Cao, Liangliang; Li, Rongjie

    2015-01-01

    Aggregation-free spherical lanthanum-doped bismuth titanate (Bi 3.25 La 0.75 Ti 3 O 12 , BLT) gel particles with an average size of about 150 nm were successfully obtained from an inverse miniemulsion sol–gel process, with Span-80 acting as surfactant, n-butanol as co-surfactant, cyclohexane as continuous phase, and submicro-droplets of aqueous solution containing Bi 3+ , La 3+ and Ti 4+ ions as dispersed phase, and then topotactically transformed into highly dispersed spherical BLT nanocrystals after an in situ crystallization at 600 °C for 8 h. It has been found that the BLT gel particles can be obtained via a moderate sol–gel reaction inside the miniemulsion droplets at 65 °C, but their morphology and aggregation degree are strongly affected by the relative amounts of Span-80 and n-butanol. The perfect spherical BLT gel particles with no aggregation can be achieved only under the condition of 3 wt% n-butanol relative to the mass of cyclohexane, with excessive amount of n-butanol leading to the formation of ill-gelled particles with irregular shapes, while insufficient addition of n-butanol resulting in terrible aggregation of gel particles. To understand the formation of aggregation-free spherical BLT gel particles, a tentative mechanism is proposed and discussed, which reveals that a well-coordinated oil–water interfacial film made up of Span-80 and n-butanol molecules and the appropriately enhanced evaporation of water from such interfaces should be responsible for the formation of aggregation-free spherical BLT gel particles. Graphical Abstract: Aggregation-free spherical BLT (Bi 3.25 La 0.75 Ti 3 O 12 ) gel particles can be prepared from an effective inverse miniemulsion sol–gel process, and subsequently topotactically transformed into spherical BLT nanocrystals through an in situ crystallization

  16. Relative bioavailability of micronized, dispersible ferric pyrophosphate added to an apple juice drink.

    Science.gov (United States)

    Roe, Mark A; Collings, Rachel; Hoogewerff, Jurian; Fairweather-Tait, Susan J

    2009-03-01

    Food iron fortification is a sustainable and relatively simple strategy to reduce/prevent iron deficiency but is a challenge for the food industry because of possible adverse organoleptic changes caused by the added iron. A micronized dispersible ferric pyrophosphate, trademarked as SunActive Fe, has recently been developed. SunActive Fe has a small particle size, is water soluble and may be suitable for fortifying liquid products. To determine the relative bioavailability of SunActive Fe and its suitability for addition to pure apple juice. Iron absorption from SunActive Fe added to pure apple juice (Minute Maid) was compared with absorption from ferrous sulphate, a highly bioavailable form of iron, in 15 women with relatively low iron stores. Both forms of iron were enriched with an iron stable isotope and iron absorption from the apple juice drinks was calculated from the isotopic enrichment of red blood cells 14 days after the last test meal. Although mean absorption of iron from SunActive Fe was significantly lower than from ferrous sulphate (5.5% compared with 9.1%), the mean bioavailability of SunActive Fe iron relative to ferrous sulphate was 0.6, indicating that it is a good source of bioavailable iron. Iron Absorption from SunActive Fe was positively correlated (r = 0.97, P = 0.01) with absorption from ferrous sulphate, and negatively correlated with serum ferritin concentration (ferrous sulphate r = -0.81, P food products.

  17. Crystal Structure of Three Compounds Related to Triphenylene and Tetracyanoquinodimethane

    DEFF Research Database (Denmark)

    Andresen, T.L.; Krebs, Frederik C; Larsen, M.

    1999-01-01

    The crystal structures of a charge-transfer complex of triphenylene with 1,3,5-tris(2,2-dicyanovinyl) benzene (1), a complex of 2,3,6,7,10,11-hexamethoxytriphenylene with 2,5-dichlorotetracyanoquinodimethane (2) and also 2,5-dichlorotetracyanoquinodimethane itself (3) have been determined. Compound...... = 83.73(3), gamma = 66.06(3)degrees. Compound 3 is monoclinic, space group I2/a (C2/c), with a = 13.692(3), b = 7.7183(15), c = 16.391(3) Angstrom, beta = 99.47(3)degrees. The structures of 1 and 2 consist of mixed stacks of donors and accepters. The structures of 2 and 3 both include 1......,2-dichlorobenzene solvent molecules. Weak hydrogen bonds are present in the structures of 1 and 2. Based on comparisons of bond lengths the electronic charge-transfer in 2 has been estimated to be about 0.3 e. The synthesis of 1,3,5-tris(2,2-dicyanovinyl) benzene is also reported....

  18. Biaxial phases in mineral liquid crystals

    NARCIS (Netherlands)

    Vroege, G.J.|info:eu-repo/dai/nl/074293001

    2013-01-01

    A review is given of liquid crystals formed in colloidal dispersions, in particular those consisting of mineral particles. Starting with the historical development and early theory, the characteristic properties related to the colloidal nature of this type of liquid crystals are discussed. The

  19. Ultrasensitive Multi-Functional Flexible Sensors Based on Organic Field-Effect Transistors with Polymer-Dispersed Liquid Crystal Sensing Layers.

    Science.gov (United States)

    Song, Myeonghun; Seo, Jooyeok; Kim, Hwajeong; Kim, Youngkyoo

    2017-06-01

    Ultrasensitive flexible sensors with multi-sensing functions are required for various applications in flexible electronics era. Here we demonstrate flexible polymer-dispersed liquid crystal (PDLC)-integrated-organic field-effect transistors (OFETs) (PDLC-i-OFETs), which sensitively respond to various stimulations including weak gas (air) flow, direct physical touch, light, and heat. The flexible PDLC-i-OFETs were fabricated by spin-coating the poly(methyl methacrylate) (PMMA)-dispersed 4,4'-pentyl-cyanobiphenyl (5CB) layers on the poly(3-hexylthiophene) (P3HT) channel layers of OFETs with 200 μm-thick poly(ethylene naphthalate) (PEN) substrates. The flexible PDLC-i-OFET devices could sense very weak nitrogen gas flow (0.3 sccm), which cannot be felt by human skins, and stably responded to direct physical touches (0.6~4.8 g load). In addition, the present devices showed very sensitive photoresponses to a visible light and exhibited excellent heat-sensing characteristics at a temperature of 25~70 °C. In particular, the present flexible PDLC-i-OFET devices could sense two different stimulations at the same time, indicative of promising multi-sensing capabilities.

  20. Spatial light modulators using polymer-dispersed liquid crystal and Bi12SiO20 photoconductive layers for projection display

    Science.gov (United States)

    Takizawa, Kuniharu; Kikuchi, Hiroshi; Fujikake, Hideo; Fujii, Takanori; Kawakita, Masahiro; Yokozawa, Minori; Murata, Akiko

    1995-04-01

    There is hopefully expected a projection display using spatial light modulators (SLMs) converting a faint input-image into a brilliant output-image. A conventional liquid crystal SLM loses more than 50% of a reading light in polarizer. To solve this problem, we developed a new SLM consisting of polymer-dispersed liquid crystal (PDLC) and Bi12SiO20 photoconductive layers. This SLM needs no polarizer, because it lets a reading light pass or scatter depending on whether a writing light is incident upon the photoconductive layer. We calculated the dependence of the resolution of the device on the several parameters including thickness, dielectric constants and conductivities of the dielectric mirror and PDLC layer by using a new electrical image method. A high-definition SLM with limiting resolution (36 - 50 lp/mm) was fabricated by stacking the optimized mirror and PDLC layer. In cooperating the device into a Schlieren optical system consisting of an LC panel as an input image source and a 1 kW Xenon lamp as a projection light source, we performed high-contrast green image projection with a total luminous flux of 1500 lumen.

  1. All-organic polymer-dispersed liquid crystal light-valves integrated with electroactive anthraquinone-2-sulfonate-doped polypyrrole thin films as driving electrodes

    International Nuclear Information System (INIS)

    Wang, Pen-Cheng; Yu, Jing-Yu; Li, Kuan-Hsun

    2011-01-01

    Highlights: → Fabrication of flexible semi-transparent all-polymer electrodes under ambient conditions without using a CVD system. → Characterization of the above electrodes based on anthraquinone-2-sulfonate-doped polypyrrole thin films. → Demonstration of all-organic liquid crystal light-valves with polypyrrole thin films as the driving electrodes. - Abstract: All-organic PDLC (polymer-dispersed liquid crystal) light-valves using all-polymer conductive substrates containing thin films of polypyrrole doped with anthraquinone-2-sulfonate (AQSA - ) as the driving electrodes were fabricated in this study. The all-polymer conductive substrates were prepared under ambient conditions by in situ depositing polypyrrole thin films on blank flexible poly(ethylene terephthalate), or PET, substrates from aqueous media in which oxidative polymerization of pyrrole was taking place. The obtained flexible all-polymer conductive substrates were semi-transparent with cohesive coatings of AQSA - doped polypyrrole thin films (thickness ∼55 nm). The all-polymer flexible conductive substrates had sheet resistivity ∼40 kΩ □ -1 and T% transparency against air ∼78% at 600 nm. The light-valves fabricated using the above all-polymer conductive substrates showed ∼50% transparency against air at 600 nm when 4 V μm -1 electric field was applied.

  2. Neutron optical potential of 28Si derived from the dispersion relation

    International Nuclear Information System (INIS)

    Kitazawa, H.; Igarasi, S.; Katsuragi, D.; Harima, Y.

    1992-01-01

    Based upon the dispersion theory, an optical potential of 28 Si was determined at the neutron energies from the Fermi energy to 20 MeV. In particular, discussion was given on a characteristic behavior of the optical potential for low-energy neutrons. Moreover, the validity of the dispersion theory was investigated for neutron single-particle bound states in 29 Si. (orig.)

  3. Leading components in forward elastic hadron scattering: Derivative dispersion relations and asymptotic uniqueness

    Science.gov (United States)

    Fagundes, D. A.; Menon, M. J.; Silva, P. V. R. G.

    2017-11-01

    Forward amplitude analyses constitute an important approach in the investigation of the energy dependence of the total hadronic cross-section σtot and the ρ parameter. The standard picture indicates for σtot a leading log-squared dependence at the highest c.m. energies, in accordance with the Froissart-Lukaszuk-Martin bound and as predicted by the COMPETE Collaboration in 2002. Beyond this log-squared (L2) leading dependence, other amplitude analyses have considered a log-raised-to-gamma form (Lγ), with γ as a real free fit parameter. In this case, analytic connections with ρ can be obtained either through dispersion relations (derivative forms), or asymptotic uniqueness (Phragmén-Lindelöff theorems). In this work, we present a detailed discussion on the similarities and mainly the differences between the Derivative Dispersion Relation (DDR) and Asymptotic Uniqueness (AU) approaches and results, with focus on the Lγ and L2 leading terms. We also develop new Regge-Gribov fits with updated dataset on σtot and ρ from pp and p¯p scattering, including all available data in the region 5 GeV-8 TeV. The recent tension between the TOTEM and ATLAS results at 7 TeV and mainly at 8 TeV is discussed and considered in the data reductions. Our main conclusions are the following: (1) all fit results present agreement with the experimental data analyzed and the goodness-of-fit is slightly better in case of the DDR approach; (2) by considering only the TOTEM data at the LHC region, the fits with Lγ indicate γ ˜ 2.0 ± 0.2 (AU approach) and γ ˜ 2.3 ± 0.1 (DDR approach); (3) by including the ATLAS data the fits provide γ ˜ 1.9 ± 0.1 (AU) and γ ˜ 2.2 ± 0.2 (DDR); (4) in the formal and practical contexts, the DDR approach is more adequate for the energy interval investigated than the AU approach. A pedagogical and detailed review on the analytic results for σtot and ρ from the Regge-Gribov, DDR and AU approaches is presented. Formal and practical

  4. The use of symmetrized valence and relative motion coordinates for crystal potentials

    DEFF Research Database (Denmark)

    McMurry, H. L.; Hansen, Flemming Yssing

    1980-01-01

    Symmetrized valence coordinates are linear combinations of conventional valence coordinates which display the symmetry of a set of atoms bound by the valence bonds. Relative motion coordinates are relative translations, or relative rotations, of two or more strongly bonded groups of atoms among...... which relatively weak forces act. They are useful for expressing interactions between molecules in molecular crystals and should be chosen, also, to reflect the symmetry of the interacting groups. Since coordinates defined by these procedures possess elements of symmetry in common with the bonding...... interaction constants coupling coordinates of unlike symmetry with regard to the crystal point group are necessarily zero. They may be small, also, for coordinates which belong to different representations of the local symmetry when this is not the same as for the crystal. Procedures are given for defining...

  5. Causality and dispersion relations and the role of the S-matrix in the ongoing research

    Energy Technology Data Exchange (ETDEWEB)

    Schroer, Bert, E-mail: schroer@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Freie Univ. , Berlin (Germany). Inst. fur Theoretische Physik

    2011-07-01

    The adaptation of the Kramers-Kronig dispersion relations to the causal localization structure of QFT led to an important project in particle physics, the only one with a successful closure. The same cannot be said about the subsequent attempts to formulate particle physics as a pure S-matrix project. The feasibility of a pure S-matrix approach are critically analyzed and their seri- ous shortcomings are highlighted. Whereas the conceptual/mathematical demands of renormalized perturbation theory are modest and misunderstandings could easily be corrected, the correct understanding about the origin of the crossing property demands the use of the mathematical theory of modular localization and its relation to the thermal KMS condition. These concepts which combine localization, vacuum polarization and thermal properties under the roof of modular theory will be explained and their use in a new constructive (nonperturbative) approach to QFT will be indicated. The S-matrix still plays a predominant role, but different from Heisenberg's and Mandelstam's proposals the new project is not a pure S-matrix approach. (author)

  6. Causality and dispersion relations and the role of the S-matrix in the ongoing research

    International Nuclear Information System (INIS)

    Schroer, Bert; Freie Univ. , Berlin

    2011-01-01

    The adaptation of the Kramers-Kronig dispersion relations to the causal localization structure of QFT led to an important project in particle physics, the only one with a successful closure. The same cannot be said about the subsequent attempts to formulate particle physics as a pure S-matrix project. The feasibility of a pure S-matrix approach are critically analyzed and their seri- ous shortcomings are highlighted. Whereas the conceptual/mathematical demands of renormalized perturbation theory are modest and misunderstandings could easily be corrected, the correct understanding about the origin of the crossing property demands the use of the mathematical theory of modular localization and its relation to the thermal KMS condition. These concepts which combine localization, vacuum polarization and thermal properties under the roof of modular theory will be explained and their use in a new constructive (nonperturbative) approach to QFT will be indicated. The S-matrix still plays a predominant role, but different from Heisenberg's and Mandelstam's proposals the new project is not a pure S-matrix approach. (author)

  7. Potential formulation of the dispersion relation for a cold, magnetized plasma

    Science.gov (United States)

    Johnson, Robert

    2012-03-01

    The derivation of the dispersion relation for a cold plasma in a constant background magnetic field is reexamined in terms of the potential formulation of electrodynamics. Under the usual approximations for a neutral plasma neglecting ion flow and thermal stress, the linearized equation of motion for the electron flow describes only the electron cyclotron resonance when the ion contribution to the material response is included through the friction term. Only by addressing the nonlinear coupling of the perturbed electron flow to the perturbed potential can a more interesting solution be found. The coupling of the flow to its potential leads to resonance in the electron fluid whose frequency depends upon the inclination of the propagation vector from the direction of the background field. The plane wave solution for general propagation vector is determined for several cases of interest and compared to the helicon relation as commonly described in the literature. The presence of an electromagnetic oscillation in an otherwise uniform plasma induces a rotation of the magnetization vector away from the axis of the background field.

  8. Multi-walled carbon nanotubes: A cytotoxicity study in relation to functionalization, dose and dispersion.

    Science.gov (United States)

    Zhou, Lulu; Forman, Henry Jay; Ge, Yi; Lunec, Joseph

    2017-08-01

    Chemical functionalization broadens carbon nanotube (CNT) applications, conferring new functions, but at the same time potentially altering toxicity. Although considerable experimental data related to CNT toxicity, at the molecular and cellular levels, have been reported, there is very limited information available for the corresponding mechanism involved (e.g. cell apoptosis and genotoxicity). The threshold dose for safe medical application in relation to both pristine and functionalized carbon nanotubes remains ambiguous. In this study, we evaluated the in vitro cytotoxicity of pristine and functionalized (OH, COOH) multi-walled carbon nanotubes (MWCNTs) for cell viability, oxidant detection, apoptosis and DNA mutations, to determine the non-toxic dose and influence of functional group in a human lung-cancer cell line exposed to 1-1000μg/ml MWCNTs for 24, 48 and 72h. The findings suggest that pristine MWCNTs induced more cell death than functionalized MWCNTs while functionalized MWCNTs are more genotoxic compared to their pristine form. The level of both dose and dispersion in the matrix used should be taken into consideration before applying further clinical applications of MWCNTs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Theoretical Re-evaluations of Scaling Relations between SMBHs and Their Host Galaxies–2. Importance of AGN Feedback Suggested by Stellar Age–Velocity Dispersion Relation

    Directory of Open Access Journals (Sweden)

    Hikari Shirakata

    2017-09-01

    Full Text Available We present the galactic stellar age—velocity dispersion relation obtained from a semi-analytic model of galaxy formation. We divide galaxies into two populations: galaxies which have over-massive/under-massive black holes (BHs against the best-fitting BH mass—velocity dispersion relation. We find that galaxies with larger velocity dispersion have older stellar ages. We also find that galaxies with over-massive BHs have older stellar ages. These results are consistent with observational results obtained from Martín-Navarro et al. (2016. We tested the model with weak AGN feedback and find that galaxies with larger velocity dispersion have a younger stellar age.

  10. Common Misconceptions about the Dynamical Theory of Crystal Lattices: Cauchy Relations, Lattice Potentials and Infinite Crystals

    Science.gov (United States)

    Elcoro, Luis; Etxebarria, Jesus

    2011-01-01

    The requirement of rotational invariance for lattice potential energies is investigated. Starting from this condition, it is shown that the Cauchy relations for the elastic constants are fulfilled if the lattice potential is built from pair interactions or when the first-neighbour approximation is adopted. This is seldom recognized in widely used…

  11. Dispersion properties of photonic bandgap guiding fibers

    DEFF Research Database (Denmark)

    Barkou, Stig Eigil; Broeng, Jes; Bjarklev, Anders Overgaard

    1999-01-01

    We investigate low-index core photonic crystal fibers. Dispersion properties very different from standard fibers are found. Both Zero dispersion are very large dispersion is shown possible at 1550 nm wavelength....

  12. Scanning Electron Microscopy Coupled with Energy Dispersive Spectrometric Analysis Reveals for the First Time Weddellite and Sylvite Crystals on the Surface of Involucral Bracts and Petals of two Xeranthemum L. (Compositae) Species.

    Science.gov (United States)

    Gavrilović, Milan; Erić, Suzana; Marin, Petar D; Garcia-Jacas, Núria; Susanna, Alfonso; Janaćković, Pedja

    2017-06-01

    In this work, weddellite and sylvite crystals are identified for the first time on the involucral bracts and petals of Xeranthemum annuum and Xeranthemum cylindraceum using scanning electron microscopy coupled with energy dispersive spectrometric (SEM-EDS) analysis. Well-developed crystals of weddellite (CaC2O4·2H2O) occur in the form of a tetragonal bipyramid (hhl), rarely in combination of a bipyramid and tetragonal prism (h00). Indumentum of involucral bracts of X. cylindraceum consists of nonglandular and glandular trichomes. Sylvite (KCl) crystals are observed only on the petal surface of X. cylindraceum. The crystals of sylvite occur in the form of perfect cubes (hexahedrons), but some crystals are deformed, i.e., partially elongated. Taxonomic significance of investigated microcharacters as well as the use of SEM-EDS analysis in taxonomic studies of plants are discussed.

  13. Relation between Raman backscattering from droplets and bulk water: Effect of refractive index dispersion

    Science.gov (United States)

    Plakhotnik, Taras; Reichardt, Jens

    2018-03-01

    A theoretical framework is presented that permits investigations of the relation between inelastic backscattering from microparticles and bulk samples of Raman-active materials. It is based on the Lorentz reciprocity theorem and no fundamental restrictions concerning the microparticle shape apply. The approach provides a simple and intuitive explanation for the enhancement of the differential backscattering cross-section in particles in comparison to bulk. The enhancement factor for scattering of water droplets in the diameter range from 0 to 60 μm (vitally important for the a priori measurement of liquid water content of warm clouds with spectroscopic Raman lidars) is about a factor of 1.2-1.6 larger (depending on the size of the sphere) than an earlier study has shown. The numerical calculations are extended to 1000 μm and demonstrate that dispersion of the refractive index of water becomes an important factor for spheres larger than 100 μm. The physics of the oscillatory phenomena predicted by the simulations is explained.

  14. Fast flavor conversions of supernova neutrinos: Classifying instabilities via dispersion relations

    Science.gov (United States)

    Capozzi, Francesco; Dasgupta, Basudeb; Lisi, Eligio; Marrone, Antonio; Mirizzi, Alessandro

    2017-08-01

    Supernova neutrinos can exhibit a rich variety of flavor conversion mechanisms. In particular, they can experience "fast" self-induced flavor conversions almost immediately above the core. Very recently, a novel method has been proposed to investigate these phenomena, in terms of the dispersion relation for the complex frequency and wave number (ω ,k ) of disturbances in the mean field of the νeνx flavor coherence. We discuss a systematic approach to such instabilities, originally developed in the context of plasma physics, and based of the time-asymptotic behavior of the Green's function of the system. Instabilities are typically seen to emerge for complex ω and can be further characterized as convective (moving away faster than they spread) and absolute (growing locally), depending on k -dependent features. Stable cases emerge when k (but not ω ) is complex, leading to disturbances damped in space, or when both ω and k are real, corresponding to complete stability. The analytical classification of both unstable and stable modes leads not only to qualitative insights about their features but also to quantitative predictions about the growth rates of instabilities. Representative numerical solutions are discussed in a simple two-beam model of interacting neutrinos. As an application, we argue that supernova and binary neutron star mergers exhibiting a "crossing" in the electron lepton number would lead to an absolute instability in the flavor content of the neutrino gas.

  15. The Riemann surface of static limit dispersion relation and projective spaces

    International Nuclear Information System (INIS)

    Majewski, M.; Meshcheryakov, V.A.; Meshcheryakov, D.V.; Tran Quang Tuyet

    2004-01-01

    The rigorous Bogolyubov's proof of the dispersion relations (DR) for pion-nucleon scattering is a good foundation for the static models. DR contain a small parameter (ratio of the pion-nucleon masses). The static models arise when this parameter goes to zero. The S-matrix in the static models has a block structure. Each block of the S-matrix has a finite order NxN and is a matrix of meromorphic functions of the light particle energy ω in the complex plane with cuts (-∞, -1], [+1,+∞). In the elastic case, it reduces to N functions S i (ω) connected by the NxN crossing-symmetry matrix A. The unitarity and the crossing symmetry are the base for the system of nonlinear boundary value problems. It defines the analytical continuation of S i (ω) from the physical sheet to the unphysical ones and can be treated as a system of nonlinear difference equations. The problem is solvable for any 2x2 crossing-symmetry matrix A that permits one to calculate the Regge trajectories for the SU(2) static model. It is shown that global analyses of this system can be carried out effectively in projective spaces P N-1 and P N . The connection between the spaces P N-1 and P N is discussed. Some particular solutions of the system are found

  16. A Mathematical Model for the Flow Resistance and the Related Hydrodynamic Dispersion Induced by River Dunes

    Directory of Open Access Journals (Sweden)

    Marilena Pannone

    2013-01-01

    Full Text Available Present work is aimed at the derivation of a simply usable equation for the total flow resistance associated with river bedforms, by a unifying approach allowing for bypassing some of the limiting restrictions usually adopted in similar types of studies. Specifically, we focused on the effect induced by the out-of-phase free surface undulations appearing in presence of sand dunes. The proposed expression, obtained by combining the balance of momentum referred to the control volume whose longitudinal dimension coincides with the dune wavelength and the energy balance integrated between its extreme sections, was tested by comparison with some laboratory experimental measurements available in the literature and referred to steady flow past fixed, variably rough bedforms. In terms of shear stress or friction factor, the proposed theory provides estimates in good agreement with the real data, especially if evaluated against the performances provided by other classical similar approaches. Moreover, when analyzed in terms of hydrodynamic dispersive properties as a function of the skin roughness on the basis of a previously derived analytical solution, the dune-covered beds seem to behave like meandering channels, responsible for a globally enhanced fluid particles longitudinal spreading, with a relatively reduced effect in the presence of less pronounced riverbed modelling.

  17. Phonon dispersion relation of uranium nitrate above and below the Neel temperature

    International Nuclear Information System (INIS)

    Dolling, G.; Holden, T.M.; Evensson, E.C.; Buyers, W.J.L.; Lander, G.H.

    1977-01-01

    Neutron coherent inelastic scattering measurements have been made of the phonon dispersion relation of uranium nitride both above and below the Neel temperature T/sub N/ = 50 K. Within the precision of the measurements, about 1% in frequency and 10% in line width and in scattered neutron intensity, no significant changes in these phonon properties were observed as a function of temperature other than those arising from population factor changes and a small stiffening of the lattice as the temperature decreases. At 4.2 K, two acoustic and two optic branches have been determined for each of the [001], [110] and [111] directions. The optic mode measurements revealed (a) a 20% variation in frequency across the Brillouin zone and (b) an interesting disposition of the LO and TO modes, such that nu/sub LO/ > nu/sub TO/ along [001] and [110], while the reverse is true along the [111] directions. Within the experimental resolution, the LO and TO modes are degenerate near q = 0. We have been unable to obtain any satisfactory description of these results on the basis of conventional theoretical treatments (e.g. rigid-ion or shell models). Other possible interpretations of the results are discussed

  18. Phonon dispersion relation of uranium nitride above and below the Neel temperature

    International Nuclear Information System (INIS)

    Dolling, G.; Holden, T.M.; Svensson, E.C.; Buyers, W.J.L.; Lander, G.H.

    1977-01-01

    Neutron coherent inelastic scattering measurements have been made of the phonon dispersion relation of uranium nitride both above and below the Neel temperature T N = 50 K. Within the precision of the measurements, about 1% in frequency and 10% in line width and in scattered neutron intensity, no significant changes in these phonon properties were observed as a function of temperature other than those arising from population factor changes and a small stiffening of the lattice as the temperature decreases. At 4.2 K, two acoustic and two optic branches have been determined for each of the [001], [110] and [111] directions. The optic mode measurements revealed (a) a 20% variation in frequency across the Brillouin zone and (b) and interesting disposition of the LO and TO modes, such that ν LO > ν TO along [001] and [11-], while the reverse is true along the [111] directions. Within the experimental resolution, the LO and TO modes are degenerate near q = 0. We have been unable to obtain any satisfactory description of these results on the basis of conventional theoretical treatments (e.g. rigid-ion or shell models). Other possible interpretations of the results are discussed. (author)

  19. Analytical study of dispersion relations for shear horizontal wave propagation in plates with periodic stubs

    KAUST Repository

    Xu, Yanlong

    2015-08-01

    The coupled mode theory with coupling of diffraction modes and waveguide modes is usually used on the calculations of transmission and reflection coefficients for electromagnetic waves traveling through periodic sub-wavelength structures. In this paper, I extend this method to derive analytical solutions of high-order dispersion relations for shear horizontal (SH) wave propagation in elastic plates with periodic stubs. In the long wavelength regime, the explicit expression is obtained by this theory and derived specially by employing an effective medium. This indicates that the periodical stubs are equivalent to an effective homogenous layer in the long wavelength. Notably, in the short wavelength regime, high-order diffraction modes in the plate and high-order waveguide modes in the stubs are considered with modes coupling to compute the band structures. Numerical results of the coupled mode theory fit pretty well with the results of the finite element method (FEM). In addition, the band structures\\' evolution with the height of the stubs and the thickness of the plate shows clearly that the method can predict well the Bragg band gaps, locally resonant band gaps and high-order symmetric and anti-symmetric thickness-twist modes for the periodically structured plates. © 2015 Elsevier B.V.

  20. Determining the near-surface current profile from measurements of the wave dispersion relation

    Science.gov (United States)

    Smeltzer, Benjamin; Maxwell, Peter; Aesøy, Eirik; Ellingsen, Simen

    2017-11-01

    The current-induced Doppler shifts of waves can yield information about the background mean flow, providing an attractive method of inferring the current profile in the upper layer of the ocean. We present measurements of waves propagating on shear currents in a laboratory water channel, as well as theoretical investigations of inversion techniques for determining the vertical current structure. Spatial and temporal measurements of the free surface profile obtained using a synthetic Schlieren method are analyzed to determine the wave dispersion relation and Doppler shifts as a function of wavelength. The vertical current profile can then be inferred from the Doppler shifts using an inversion algorithm. Most existing algorithms rely on a priori assumptions of the shape of the current profile, and developing a method that uses less stringent assumptions is a focus of this study, allowing for measurement of more general current profiles. The accuracy of current inversion algorithms are evaluated by comparison to measurements of the mean flow profile from particle image velocimetry (PIV), and a discussion of the sensitivity to errors in the Doppler shifts is presented.

  1. CALIBRATING STELLAR VELOCITY DISPERSIONS BASED ON SPATIALLY RESOLVED H-BAND SPECTRA FOR IMPROVING THE MBH-σ* RELATION

    International Nuclear Information System (INIS)

    Kang, Wol-Rang; Woo, Jong-Hak; Park, Daeseong; Schulze, Andreas; Riechers, Dominik A.; Kim, Sang Chul; Smolcic, Vernesa

    2013-01-01

    To calibrate stellar velocity dispersion measurements from optical and near-IR stellar lines, and to improve the black hole mass (M BH )-stellar velocity dispersion (σ * ) relation, we measure σ * based on high-quality H-band spectra for a sample of 31 nearby galaxies, for which dynamical M BH is available in the literature. By comparing velocity dispersions measured from stellar lines in the H-band with those measured from optical stellar lines, we find no significant difference, suggesting that optical and near-IR stellar lines represent the same kinematics and that dust effect is negligible for early-type galaxies. Based on the spatially resolved rotation and velocity dispersion measurements along the major axis of each galaxy, we find that a rotating stellar disk is present for 80% of galaxies in the sample. For galaxies with a rotation component, σ * measured from a single aperture spectrum can vary by up to ∼20%, depending on the size of the adopted extraction aperture. To correct for the rotational broadening, we derive luminosity-weighted σ * within the effective radius of each galaxy, providing uniformly measured velocity dispersions to improve the M BH -σ * relation.

  2. Acousto-optical phonon excitation in piezoelectric wurtzite slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Duggen, Lars; Willatzen, Morten

    2017-01-01

    This paper presents a theoretical investigation of phonon dispersion in piezoelectric slabs of hexagonal crystal symmetry (wurtzite). Specifically we solve the fully coupled dispersion relations in a GaN free standing quantum well by varying the crystal growth direction from the [001] axis...

  3. Effects of weak nonlinearity on the dispersion relation and frequency band-gaps of a periodic Bernoulli–Euler beam

    DEFF Research Database (Denmark)

    Sorokin, Vladislav S.; Thomsen, Jon Juel

    2016-01-01

    The paper deals with analytically predicting the effects of weak nonlinearity on the dispersion relation and frequency band-gaps of a periodic Bernoulli– Euler beam performing bending oscillations. Two cases are considered: (i) large transverse deflections, where nonlinear (true) curvature...

  4. Phonon dispersion relations in PrBa2Cu3O6+x (x approximate to 0.2)

    DEFF Research Database (Denmark)

    Gardiner, C.H.; Boothroyd, A.T.; Larsen, B.H.

    2004-01-01

    We report measurements of the phonon dispersion relations in nonsuperconducting, oxygen-deficient PrBa2Cu3O6+x (xapproximate to0.2) by inelastic neutron scattering. The data are compared with a model of the lattice dynamics based on a common interatomic potential. Good agreement is achieved for all...

  5. Applying the cold plasma dispersion relation to whistler mode chorus waves: EMFISIS wave measurements from the Van Allen Probes.

    Science.gov (United States)

    Hartley, D P; Chen, Y; Kletzing, C A; Denton, M H; Kurth, W S

    2015-02-01

    Most theoretical wave models require the power in the wave magnetic field in order to determine the effect of chorus waves on radiation belt electrons. However, researchers typically use the cold plasma dispersion relation to approximate the magnetic wave power when only electric field data are available. In this study, the validity of using the cold plasma dispersion relation in this context is tested using Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) observations of both the electric and magnetic spectral intensities in the chorus wave band (0.1-0.9 f ce ). Results from this study indicate that the calculated wave intensity is least accurate during periods of enhanced wave activity. For observed wave intensities >10 -3 nT 2 , using the cold plasma dispersion relation results in an underestimate of the wave intensity by a factor of 2 or greater 56% of the time over the full chorus wave band, 60% of the time for lower band chorus, and 59% of the time for upper band chorus. Hence, during active periods, empirical chorus wave models that are reliant on the cold plasma dispersion relation will underestimate chorus wave intensities to a significant degree, thus causing questionable calculation of wave-particle resonance effects on MeV electrons.

  6. Left-cut contribution to the dispersion relation for the elastic electron - atomic-hydrogen scattering amplitude

    International Nuclear Information System (INIS)

    Amusia, M.Ya.; Kuchiev, M.Yu.

    1979-01-01

    The jump in the electron - atomic-hydrogen forward scattering amplitude at the cut extending to the left from E = -0.5 au is calculated as a function of the incident electron energy, E, by using the second Born approximation. The contribution from this singularity to the dispersion relation is determined. (Auth.)

  7. Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

    NARCIS (Netherlands)

    Dosio, A.; Vilà-Guerau de Arellano, J.

    2006-01-01

    The influence of the different scales of turbulent motion on plume dispersion in the atmospheric convective boundary layer (CBL) is studied by means of a large-eddy simulation (LES). In particular, the large-scale (meandering) and small-scale (relative diffusion) contributions are separated by

  8. Crystal methamphetamine and ecstasy differ in relation to unsafe sex among young gay men.

    Science.gov (United States)

    Schilder, Arn J; Lampinen, Thomas M; Miller, Mary Lou; Hogg, Robert S

    2005-01-01

    Poly-substance use in gay social ('club') settings is common. Recent studies suggest a link between 'club' drug use and sexual risk behaviours. In this qualitative study, we compare and contrast two 'club' drugs: crystal methamphetamine and ecstasy (MDMA). Life history interviews were conducted with 12 HIV seroconverters and 12 age-matched controls recruited from a prospective cohort study of young gay and bisexual men in Vancouver, British Columbia. Textual data concerning illicit substance use and unsafe sex were analyzed using NUDIST software. Most men related a substantial knowledge of and experience with crystal and ecstasy. Both drugs had attributes that enhanced gay socialization and were used in the same venues. Crystal was used to remain awake and increase energy. Ecstasy was used to induce euphoria and group connectedness. However, unlike ecstasy, crystal was associated with a distinct pattern of sexual arousal that frequently included unprotected (sometimes group) sex, was more likely to be used regularly by HIV-positive men, and was reportedly highly addictive and problematic. Crystal and ecstasy are used in the same social venues but differ markedly in relation to sexual risk behaviour.

  9. Crystallization speed of salbutamol as a function of relative humidity and temperature.

    Science.gov (United States)

    Zellnitz, Sarah; Narygina, Olga; Resch, Christian; Schroettner, Hartmuth; Urbanetz, Nora Anne

    2015-07-15

    Spray dried salbutamol sulphate and salbutamol base particles are amorphous as a result of spray drying. As there is always the risk of recrystallization of amorphous material, the aim of this work is the evaluation of the temperature and humidity dependent recrystallization of spray dried salbutamol sulphate and base. Therefore in-situ Powder X-ray Diffraction (PXRD) studies of the crystallization process at various temperature (25 and 35 °C) and humidity (60%, 70%, 80%, 90% relative humidity) conditions were performed. It was shown that the crystallization speed of salbutamol sulphate and base is a non-linear function of both temperature and relative humidity. The higher the relative humidity the higher is the crystallization speed. At 60% relative humidity salbutamol base as well as salbutamol sulphate were found to be amorphous even after 12 h, however samples changed optically. At 70% and 90% RH recrystallization of salbutamol base is completed after 3 h and 30 min and recrystallization of salbutamol sulphate after 4h and 1h, respectively. Higher temperature (35 °C) also leads to increased crystallization speeds at all tested values of relative humidity. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Kinetic transverse dispersion relation for relativistic magnetized electron-positron plasmas with Maxwell-Jüttner velocity distribution functions

    International Nuclear Information System (INIS)

    López, Rodrigo A.; Moya, Pablo S.; Muñoz, Víctor; Viñas, Adolfo F.; Valdivia, J. Alejandro

    2014-01-01

    We use a kinetic treatment to study the linear transverse dispersion relation for a magnetized isotropic relativistic electron-positron plasma with finite relativistic temperature. The explicit linear dispersion relation for electromagnetic waves propagating along a constant background magnetic field is presented, including an analytical continuation to the whole complex frequency plane for the case of Maxwell-Jüttner velocity distribution functions. This dispersion relation is studied numerically for various temperatures. For left-handed solutions, the system presents two branches, the electromagnetic ordinary mode and the Alfvén mode. In the low frequency regime, the Alfvén branch has two dispersive zones, the normal zone (where ∂ω/∂k > 0) and an anomalous zone (where ∂ω/∂k < 0). We find that in the anomalous zone of the Alfvén branch, the electromagnetic waves are damped, and there is a maximum wave number for which the Alfvén branch is suppressed. We also study the dependence of the Alfvén velocity and effective plasma frequency with the temperature. We complemented the analytical and numerical approaches with relativistic full particle simulations, which consistently agree with the analytical results

  11. Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

    DEFF Research Database (Denmark)

    Ferrari, Andrea C.; Bonaccorso, Francesco; Falko, Vladimir

    2015-01-01

    We present the science and technology roadmap (STR) for graphene, related twodimensional (2d) crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. The roadmap was developed within the framework of the Euro...

  12. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  13. Hydrological dispersion of radioactive material in relation to nuclear power plant siting

    International Nuclear Information System (INIS)

    1985-01-01

    This Guide discusses the dispersion of normal and accidental releases of radioactive materials from nuclear power plants into surface water, including the washout of airborne radionuclides, and gives recommendations on information to be collected during the various stages of the siting procedure, a minimum measurement programme and the selection and validation of appropriate mathematical models for predicting dispersion. Guidelines are also provided for the optimal use of models for a specific site situation and for defining the necessary input parameters. Results of existing validation studies are given

  14. Dispersion Relations for Isothermal Plasma around the Horizon of Reissner–Nordström–de Sitter Black Hole

    International Nuclear Information System (INIS)

    Hasan, M. Khayrul; Ali, M. Hossain

    2009-01-01

    We formulate the general relativistic magnetohydrodynamic equations for isothermal plasma in spatially flat Reissner–Nordström–de Sitter metric by using 3+1 split of spacetime. Respective perturbed equations are linearized for rotating magnetized surroundings. These are then Fourier analyzed and the corresponding dispersion relations are obtained. These relations are discussed both analytically and numerically in order to investigate the nature of waves with positive angular frequency around the horizon

  15. The Mean and Scatter of the Velocity Dispersion-Optical Richness Relation for MaxBCG Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Becker, M.R.; McKay, T.A.; /Michigan U.; Koester, B.; /Chicago U., Astron. Astrophys. Ctr.; Wechsler, R.H.; /KIPAC, Menlo Park /SLAC /Stanford U., Phys. Dept.; Rozo, E.; /Ohio State U.; Evrard, A.; /Michigan U. /Michigan U., MCTP; Johnston, D.; /Caltech, JPL; Sheldon, E.; /New York U.; Annis, J.; /Fermilab; Lau, E.; /Chicago U., Astron. Astrophys. Ctr.; Nichol, R.; /Portsmouth U., ICG; Miller, C.; /Michigan U.

    2007-06-05

    The distribution of galaxies in position and velocity around the centers of galaxy clusters encodes important information about cluster mass and structure. Using the maxBCG galaxy cluster catalog identified from imaging data obtained in the Sloan Digital Sky Survey, we study the BCG--galaxy velocity correlation function. By modeling its non-Gaussianity, we measure the mean and scatter in velocity dispersion at fixed richness. The mean velocity dispersion increases from 202 {+-} 10 km s{sup -1} for small groups to more than 854 {+-} 102 km s{sup -1} for large clusters. We show the scatter to be at most 40.5{+-}3.5%, declining to 14.9{+-}9.4% in the richest bins. We test our methods in the C4 cluster catalog, a spectroscopic cluster catalog produced from the Sloan Digital Sky Survey DR2 spectroscopic sample, and in mock galaxy catalogs constructed from N-body simulations. Our methods are robust, measuring the scatter to well within one-sigma of the true value, and the mean to within 10%, in the mock catalogs. By convolving the scatter in velocity dispersion at fixed richness with the observed richness space density function, we measure the velocity dispersion function of the maxBCG galaxy clusters. Although velocity dispersion and richness do not form a true mass--observable relation, the relationship between velocity dispersion and mass is theoretically well characterized and has low scatter. Thus our results provide a key link between theory and observations up to the velocity bias between dark matter and galaxies.

  16. Highly dispersed spherical Bi3.25La0.75Ti3O12 nanocrystals via topotactic crystallization of aggregation-free gel particles from an effective inverse miniemulsion sol-gel approach

    Science.gov (United States)

    Wang, Aijun; Zeng, Yanwei; Han, Longxiang; Ding, Chuan; Cao, Liangliang; Li, Rongjie

    2015-09-01

    Aggregation-free spherical lanthanum-doped bismuth titanate (Bi3.25La0.75Ti3O12, BLT) gel particles with an average size of about 150 nm were successfully obtained from an inverse miniemulsion sol-gel process, with Span-80 acting as surfactant, n-butanol as co-surfactant, cyclohexane as continuous phase, and submicro-droplets of aqueous solution containing Bi3+, La3+ and Ti4+ ions as dispersed phase, and then topotactically transformed into highly dispersed spherical BLT nanocrystals after an in situ crystallization at 600 °C for 8 h. It has been found that the BLT gel particles can be obtained via a moderate sol-gel reaction inside the miniemulsion droplets at 65 °C, but their morphology and aggregation degree are strongly affected by the relative amounts of Span-80 and n-butanol. The perfect spherical BLT gel particles with no aggregation can be achieved only under the condition of 3 wt% n-butanol relative to the mass of cyclohexane, with excessive amount of n-butanol leading to the formation of ill-gelled particles with irregular shapes, while insufficient addition of n-butanol resulting in terrible aggregation of gel particles. To understand the formation of aggregation-free spherical BLT gel particles, a tentative mechanism is proposed and discussed, which reveals that a well-coordinated oil-water interfacial film made up of Span-80 and n-butanol molecules and the appropriately enhanced evaporation of water from such interfaces should be responsible for the formation of aggregation-free spherical BLT gel particles.

  17. Enhanced two-channel nonlinear imaging by a highly polarized supercontinuum light source generated from a nonlinear photonic crystal fiber with two zero-dispersion wavelengths

    Science.gov (United States)

    Tao, Wei; Bao, Hongchun; Gu, Min

    2011-05-01

    Real-time monitoring the variation of chlorophyll distributions and cellular structures in leaves during plant growth provides important information for understanding the physiological statuses of plants. Two-photon-excited autofluorescence imaging and second harmonic generation imaging of leaves can be used for monitoring the nature intrinsic fluorophores distribution and cellular structures of leaves by the use of the near-infrared region of light which has minimal light absorption by endogenous molecules and thus increases tissue penetration. However, the two-photon absorption peak of intrinsic fluorophores of a ficus benjamina leaf is 50 nm away from the second harmonic generation excitation wavelength, which cannot be effectively excited by a femtosecond laser beam with one central wavelength. This paper shows that a highly polarized supercontinuum light generated from a birefringent nonlinear photonic crystal fiber with two zero-dispersion wavelengths can effectively excite two-photon autofluorescence as well as second harmonic generation signals for simultaneously monitoring intrinsic fluorophore distributions and non-centrosymmetric structures of leaves.

  18. Measurement of surface phonon dispersion relations for LiF, NaF, and KCl through energy-analysed inelastic scattering of a helium atomic beam

    International Nuclear Information System (INIS)

    Doak, R.B.

    1981-01-01

    A crystal surface terminates abruptly one dimension of lattice periodicity, constituting a lattice defect with concomitant localized modes of vibration, termed surface phonons. Such surface phonons have previously been investigated in the long wavelength, non-dispersive regime. The present work reports the first observation of surface phonons in the short wavelength, dispersive range. The data allow for the first time a surface phonon dispersion curve to be plotted completely from origin to edge of the surface Brillouin zone. Measurements were made of phonons along the (anti GAMMA anti M) and (anti GAMMA anti X) azimuths of the LiF(001) surface and along the azimuth of NaF(001) and KC1(001) surfaces. The results are in substantial agreement with theoretical predictions, although for LiF the measured Rayleigh dispersion curve at M lies appreciably below the theoretical value, possibly reflecting the effects of surface relaxation. (orig.)

  19. Anisotropy of hardness and laser damage threshold of unidirectional organic NLO crystal in relation to the internal structure

    International Nuclear Information System (INIS)

    Natarajan, V.; Arivanandhan, M.; Sankaranarayanan, K.; Hayakawa, Y.

    2011-01-01

    Highlights: · Growth rate of the unidirectional organic crystals were measured and the variation in the growth rate was explained based on the attachment energy model. · Anisotropic behaviors of hardness and laser damage threshold of the unidirectional materials were analyzed. · The obtained results were explained based on the crystal structure of the material. - Abstract: Unidirectional benzophenone crystals were grown along , and directions by uniaxially solution crystallization method at ambient temperature. The growth rate of the grown crystals was varied with orientation. The optical absorption coefficients of benzophenone were measured as a function of wavelength. The optical absorption study reveals that the benzophenone crystal has very low absorption in the wavelength range of interest. Moreover, the laser damage threshold and micro hardness for , and oriented unidirectional benzophenone crystals were measured using a Q-switched Nd:YAG laser operating at 1064 nm radiation and Vicker's micro hardness tester, respectively. The laser damage threshold is larger for the and oriented crystals compared to oriented crystal at 1064 nm wavelength. The result is consistent with the hardness variation observed for the three different crystallographic directions of benzophenone crystal. The relation between the laser damage profile and mechanical hardness anisotropy is discussed based on the crystal structure of benzophenone.

  20. Effects of weak nonlinearity on the dispersion relation and frequency band-gaps of a periodic Bernoulli-Euler beam.

    Science.gov (United States)

    Sorokin, Vladislav S; Thomsen, Jon Juel

    2016-02-01

    The paper deals with analytically predicting the effects of weak nonlinearity on the dispersion relation and frequency band-gaps of a periodic Bernoulli-Euler beam performing bending oscillations. Two cases are considered: (i) large transverse deflections, where nonlinear (true) curvature, nonlinear material and nonlinear inertia owing to longitudinal motions of the beam are taken into account, and (ii) mid-plane stretching nonlinearity. A novel approach is employed, the method of varying amplitudes. As a result, the isolated as well as combined effects of the considered sources of nonlinearities are revealed. It is shown that nonlinear inertia has the most substantial impact on the dispersion relation of a non-uniform beam by removing all frequency band-gaps. Explanations of the revealed effects are suggested, and validated by experiments and numerical simulation.

  1. Influence of Complete Coriolis Force on the Dispersion Relation of Ocean Internal-wave in a Background Currents Field

    Directory of Open Access Journals (Sweden)

    Liu Yongjun

    2015-01-01

    Full Text Available In this thesis, the influence of complete Coriolis force (the model includes both the vertical and horizontal components of Coriolis force on the dispersion relation of ocean internal-wave under background currents field are studied, it is important to the study of ocean internal waves in density-stratified ocean. We start from the control equation of sea water movement in the background of the non-traditional approximation, and the vertical velocity solution is derived where buoyancy frequency N(z gradually varies with the ocean depth z. The results show that the influence of complete Coriolis force on the dispersion relation of ocean internal-wave under background currents field is obvious, and these results provide strong evidence for the understanding of dynamic process of density stratified ocean internal waves.

  2. Dispersion relations for hadronic light-by-light scattering and the muon g - 2

    Science.gov (United States)

    Procura, Massimiliano; Colangelo, Gilberto; Hoferichter, Martin; Stoffer, Peter

    2018-01-01

    The largest uncertainties in the Standard Model calculation of the anomalous magnetic moment of the muon (g - 2)μ come from hadronic effects, and in a few years the subleading hadronic light-by-light (HLbL) contribution might dominate the theory error. We present a dispersive description of the HLbL tensor, which is based on unitarity, analyticity, crossing symmetry, and gauge invariance. This opens up the possibility of a data-driven determination of the HLbL contribution to (g - 2)μ with the aim of reducing model dependence and achieving a reliable error estimate. Our dispersive approach defines unambiguously the pion-pole and the pion-box contribution to the HLbL tensor. Using Mandelstam double-spectral representation, we have proven that the pion-box contribution coincides exactly with the one-loop scalar-QED amplitude, multiplied by the appropriate pion vector form factors. Using dispersive fits to high-statistics data for the pion vector form factor, we obtain . A first model-independent calculation of effects of ππ intermediate states that go beyond the scalar-QED pion loop is also presented. We combine our dispersive description of the HLbL tensor with a partial-wave expansion and demonstrate that the known scalar-QED result is recovered after partial-wave resummation. After constructing suitable input for the γ*γ* → ππ helicity partial waves based on a pion-pole left-hand cut (LHC), we find that for the dominant charged-pion contribution this representation is consistent with the two-loop chiral prediction and the COMPASS measurement for the pion polarizability. This allows us to reliably estimate S-wave rescattering effects to the full pion box and leads to .

  3. Designing large-bandwidth planar photonic crystal waveguides

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Søndergaard, Thomas

    2002-01-01

    Our waveguide design is characterized by first of all a large bandwidth, and secondly it is characterized by a relatively high group velocity giving a better modal dispersion match with the modes of standard waveguides used for coupling light into the planar crystal waveguide (PCW). We consider t...... the dispersion properties for a PCW based on introducing a line defect in a photonic crystal with air-holes arranged periodically on a triangular lattice in silicon....

  4. [Pharmacokinetics and relative bioavailability of THC and THC-solid dispersion orally to mice at single dose].

    Science.gov (United States)

    Liao, Li; Hua, Hua; Zhao, Jun-Ning; Luo, Heng; Yang, An-Dong

    2014-03-01

    To establish a fast sensitive, reproducible LC-MS/MS method to study pharmacokinetic properties of THC, and compare relative bioavailability of THC and its solid dispersion in mice. 200 mice were divided randomly into two groups, and administered orally with THC and THC-solid dispersion after fasting (calculate on THC:400 mg x kg(-1)), used HPLC-MS/MS method to determine the THC concentration of each period at the following times: baseline ( predose ), 15, 30, 45 min, 1, 1.5, 2, 3, 4, 6, 24 h after dosing. Calculating the pharmacokinetic parameters according to the C-t curv, and then use the Phoenix WinNonlin software for data analysis. The calibration curves were linear over the range 9.06-972 microg x L(-1) for THC (R2 = 0.999). The limit of detection (LOD) was 0.7 microg x L(-1), respectively. The average extraction recoveries for THC was above 75%, The methodology recoveries were between 79% and 108%. The intra-day and inter-day RSD were less than 13%, the stability test showed that the plasma samples was stable under different conditions (RSD THC and THC-solid dispersion orally to mice shows as fllows: T(max), were 60 and 15 min, AUC(0-t) were 44 500.43 and 57 497.81 mg x L(-1) x min, AUC(0-infinity) were 51 226.00 and 68 031.48 mg x L(-1) x min, MRT(0-infinity) were 596.915 6, 661.747 7 min, CL(z)/F were 0.007 809 and 0.005 88 L x min(-1) x kg(-1). Compared with THC, the MRT and t1/2 of the THC-solid dispersion were all slightly extended, the t(max) was significantly reduced, AUC(0-24 h), AUC(0-infinity) and C(max) were all significantly higher, the relative bioavailability of THC-solid dispersion is 1.34 times of THC. The results of the experiment shows that the precision, accuracy, recovery and applicability were found to be adequate for the pharmacokinetic studies. After oral administration to mice, the relative bioavailability of THC-solid dispersion show significant improvement compared to THC.

  5. Crystal growth of ZnSe and related ternary compound semiconductors by physical vapor transport

    Science.gov (United States)

    Su, Ching-Hua

    1993-01-01

    The materials to be investigated are ZnSe and related ternary semiconducting alloys (e.g., ZnS(x)Se(1-x), ZnTe(x)Se(1-x), and Zn(1-x)Cd(x)Se). These materials are useful for opto-electronic applications such as high efficient light emitting diodes and low power threshold and high temperature lasers in the blue-green region of the visible spectrum. The recent demonstration of its optical bistable properties also makes ZnSe a possible candidate material for digital optical computers. The investigation consists of an extensive ground-based study followed by flight experimentation, and involves both experimental and theoretical work. The objectives of the ground-based work are to establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low gravity environment and to obtain the experimental data and perform the analyses required to define the optimum parameters for the flight experiments. During the six months of the Preliminary Definition Phase, the research efforts were concentrated on the binary compound ZnSe - the purification of starting materials of Se by zone refining, the synthesis of ZnSe starting materials, the heat treatments of the starting materials, the vapor transport rate measurements, the vapor partial pressure measurements of ZnSe, the crystal growth of ZnSe by physical vapor transport, and various characterization on the grown ZnSe crystals.

  6. A new photonic crystal fiber design on the high negative ultra-flattened dispersion for both X and Y polarization modes

    DEFF Research Database (Denmark)

    Mahmud, Russel Reza; Razzak, S. M Abdur; Hasan, Md Imran

    2016-01-01

    . The guiding properties are observed by employing a circular perfectly matched layer (PML) boundary through the finite-element method (FEM). The proposed design is compatible for the application of residual dispersion compensation (RDC) as it grants negative dispersion (ND) and very low scale dispersion...

  7. Phase I Trial of 2-Methoxyestradiol (2ME2, Panzem®) NanoCrystal® Dispersion (NCD®) in Advanced Solid Malignancies

    Science.gov (United States)

    Tevaarwerk, Amye J.; Holen, Kyle D.; Alberti, Dona B.; Sidor, Carolyn; Arnott, Jamie; Quon, Check; Wilding, George; Liu, Glenn

    2010-01-01

    Purpose 2-methoxyestradiol (2ME2, Panzem®) is an endogenous, estradiol-17β metabolite which at pharmacological doses exerts antimitotic and antiangiogenic activities. Studies with a 2ME2 capsule formulation showed limited oral bioavailability. We report the results of a phase I study using a NanoCrystal® Dispersion formulation of 2ME2 (2ME2 NCD). Experimental Design Patients with refractory solid tumors received 2ME2 NCD orally. Patients received drug either every six hours (Part A) or every eight hours (Part B). Doses were escalated in successive cohorts until the maximum-tolerated dose (MTD) was identified. The primary objective was identifying the MTD. Secondary objectives were to evaluate the plasma pharmacokinetics of 2ME2 and efficacy. Results In Part A, 16 patients received a median of 4 cycles of 2ME2 NCD. DLTs included fatigue (2), hypophosphatemia (2), increased ALT (1) and muscle weakness (1). Trough levels at steady state reached the minimum effective concentration in all cohorts. The MTD was determined to be 1000 mg orally every 6 hours. In Part B, 10 patients received a median of 1 cycle. DLTs included elevated γ‐glutamyltransferase (1), hyponatremia (1), fatigue (1), and anorexia (1). An MTD could not be defined for Part B, because 4/10 patients had DLTs at the initial dose level and dose reduction was not pursued. Thirteen patients had stable disease (A: 11, B: 2); there were no confirmed responses. Conclusion For 2ME2 NCD, the MTD and recommended phase II regimen is 1000 mg orally every 6 hours. Treatment was generally well tolerated. PMID:19228747

  8. Wide-band and fast wavelength-swept optical parametric oscillator with a photonic crystal fiber based on dispersion tuning technology at 1 μm

    Science.gov (United States)

    Chen, Jin; Yang, Sigang; Guo, Qiang; Chen, Hongwei; Chen, Minghua; Xie, Shizhong

    2016-03-01

    A wavelength-swept fiber optical parametric oscillator (FOPO) based on dispersion tuning technology at wavelength around 1 μm is demonstrated. A continuous wave single-longitudinal-mode ytterbium doped fiber laser with a line-width of 0.05 nm is modulated through a LiNbO3 Mach-Zehnder modulator to be a pulsed source with variable repetition rate. The pulsed source is amplified with a two-stage ytterbium doped fiber amplifier (YDFA) to a mediate power and a high power YDFA to peak power higher than 40 W. And a homemade 50-m photonic crystal fiber (PCF) which provides the optical parametric gain is pumped by the pulsed source. The optical modulator is driven by a frequency-swept electrical clock signal with frequency ranges from 107.24 MHz to 107.31 MHz. Thus the FOPO generates a wavelength-swept light source with a range of 80 nm centered at 1065.10 nm. Through careful customizing the sweeping rate of the driving clock signal, the sweeping rate of the parametric oscillator can be up to 10 kHz, which is limited by currently used electrical sweeping source. The generated pulses train are with pulse width of about 110 ps. For the electrical scan is used instead of the traditional mechanical scanning method in conventional wavelength-swept sources, it performs better stability under prolonged operation. The wavelength-swept FOPO is potential to be applied in OCT systems for its good stability and advantaged wavelength band.

  9. Investigation of magnon dispersion relations and neutron scattering cross sections with special attention to anisotropy effects

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker; Kowalska, A.; Laut, Peter

    1967-01-01

    A general bilinear two-Bose Hamiltonian is diagonalized and the result used in a discussion of non-imteracting spin waves in a two-sub-lattice ferromagnet having not negligible anisotropy in the spin interaction. Model-independent functions suitable for the analysis of experimental dispersion...... curves are suggested. The magnon cross section for unpolarized neutrons is calculated and shown to be dependent on the anisotropy in the spin interaction. Thus in principle it allows the detection of anisotropy in the exchange interaction. Some remarks are made concerning antiferromagnetic and plane...

  10. Polymer Dispersed Liquid Crystal Displays

    Science.gov (United States)

    Doane, J. William

    The following sections are included: * INTRODUCTION AND HISTORICAL DEVELOPMENT * PDLC MATERIALS PREPARATION * Polymerization induced phase separation (PIPS) * Thermally induced phase separation (TIPS) * Solvent induced phase separation (SIPS) * Encapsulation (NCAP) * RESPONSE VOLTAGE * Dielectric and resistive effects * Radial configuration * Bipolar configuration * Other director configurations * RESPONSE TIME * DISPLAY CONTRAST * Light scattering and index matching * Incorporation of dyes * Contrast measurements * PDLC DISPLAY DEVICES AND INNOVATIONS * Reflective direct view displays * Large-scale, flexible displays * Switchable windows * Projection displays * High definition spatial light modulator * Haze-free PDLC shutters: wide angle view displays * ENVIRONMENTAL STABILITY * ACKNOWLEDGEMENTS * REFERENCES

  11. Equatorward dispersion of the Sarychev volcanic plume and the relation to the Asian summer monsoon

    Science.gov (United States)

    Wu, Xue; Griessbach, Sabine; Hoffmann, Lars

    2017-04-01

    Sulfur dioxide emissions and subsequent sulfate aerosols from strong volcanic eruptions have large impact on global climate. Although most of previous studies attribute the global influence to volcanic eruptions in the tropics, high-latitude volcanic eruptions are also an important cause for global climate variations. In fact, the potential climate impact of volcanic also largely depends on the season when eruptions occur, the erupted plume height and the surrounding meteorological conditions. This work focuses on the eruption of a high-latitude volcano Sarychev, and the role of Asian summer monsoon (ASM) during the transport and dispersion of the erupted plumes. First, the sulfur dioxide emission rate and height of emission of the Sarychev eruption in June 2009 are modelled using a Lagrangian particle dispersion model named Massive-Parallel Trajectory Calculations (MPTRAC), together with sulfur dioxide observations of the Atmospheric Infrared Sounder (AIRS/Aqua) and a backward trajectory approach. Then, the transport and dispersion of the plumes are modelled with MPTRAC and validated with sulfur dioxide observations from AIRS and aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The modelled trajectories and the MIPAS data both show the plumes are transported towards the tropics from the southeast edge of the ASM (in the vertical range of 340-400K) controlled by the clockwise winds of ASM, and from above the ASM (above 400K) in form of in-mixing process. Especially, in the vertical range around 340-400K, a transport barrier based on potential vorticity (PV) gradients separates the 'aerosol hole' inside of the ASM circulation and the aerosol-rich surrounding area, which shows the PV gradients based barrier may be more practical than the barrier based on the geopotential height. With help of ASM circulation, the aerosol transported to the tropics and stayed in the tropical lower stratosphere for about eight months

  12. The Cluster-EAGLE project: velocity bias and the velocity dispersion-mass relation of cluster galaxies

    Science.gov (United States)

    Armitage, Thomas J.; Barnes, David J.; Kay, Scott T.; Bahé, Yannick M.; Dalla Vecchia, Claudio; Crain, Robert A.; Theuns, Tom

    2018-03-01

    We use the Cluster-EAGLE simulations to explore the velocity bias introduced when using galaxies, rather than dark matter particles, to estimate the velocity dispersion of a galaxy cluster, a property known to be tightly correlated with cluster mass. The simulations consist of 30 clusters spanning a mass range 14.0 ≤ log10(M200 c/M⊙) ≤ 15.4, with their sophisticated subgrid physics modelling and high numerical resolution (subkpc gravitational softening), making them ideal for this purpose. We find that selecting galaxies by their total mass results in a velocity dispersion that is 5-10 per cent higher than the dark matter particles. However, selecting galaxies by their stellar mass results in an almost unbiased (<5 per cent) estimator of the velocity dispersion. This result holds out to z = 1.5 and is relatively insensitive to the choice of cluster aperture, varying by less than 5 per cent between r500 c and r200 m. We show that the velocity bias is a function of the time spent by a galaxy inside the cluster environment. Selecting galaxies by their total mass results in a larger bias because a larger fraction of objects have only recently entered the cluster and these have a velocity bias above unity. Galaxies that entered more than 4 Gyr ago become progressively colder with time, as expected from dynamical friction. We conclude that velocity bias should not be a major issue when estimating cluster masses from kinematic methods.

  13. Analysis of patterns of dispersion of intertidal prosobranch gastropods in relation to macroalgae and rock-pools.

    Science.gov (United States)

    Underwood, A J

    1976-06-01

    The patterns of dispersion of Nerita atramentosa, Austrocochlea constricta, Bembicium nanum and Cellana tramoserica are analysed from quadrat samples taken between June 1972 and June 1973. In each quadrat, the proportion of animals in each of two substrata, the encrusting alga Peyssonelia gunniana and small pools, was recorded, with the proportional area of cover of each substratum, height on the shore, density of the species and the time of sampling. Multiple regression and covariance analysis showed that, in all cases, there was a linear relationship between proportion in a substratum and proportional area of substratum. No other variables were significant.Juvenile Nerita and Austrocochlea showed preferences for both substrata. Adult Nerita and all Bembicium were dispersed at random with respect to both substrata. Adult Austrocochlea were randomly dispersed with respect to Peyssonelia, but showed a preference for water. Cellana showed a preference for water and against Peyssonelia. These microhabitat preferences are discussed in relation to previously described effects of substrata on the densities of these four species.

  14. Lectures on Dispersion Theory

    Science.gov (United States)

    Salam, A.

    1956-04-01

    Lectures with mathematical analysis are given on Dispersion Theory and Causality and Dispersion Relations for Pion-nucleon Scattering. The appendix includes the S-matrix in terms of Heisenberg Operators. (F. S.)

  15. Evidence for evanescent waves at interfaces in a high-index prism/liquid-crystal-Au-NPs/glass/air structure and effects of relative concentration of gold nanoparticles, wavelength, polarization, and incident angle of the laser beam

    Science.gov (United States)

    Tiwari, Kunal; Singh, Ankit; Sharma, Suresh

    2011-10-01

    Incorporation of relatively small concentrations of gold nanoparticles (Au NPs) in a polymer-dispersed liquid crystal (PDLC) is known to lower the operating threshold voltage and increase optical transmission through the device.ootnotetextA. Hinojosa and S. C. Sharma, Applied Physics Letters, 97, 081114 (2010) In order to understand whether there is an interplay between the localized surface plasmon resonance at Au-NPs-dielectric interfaces and the electro-optical properties of PDLC devices, we have investigated propagation of light through a high-index prism/liquid-crystal-Au-NPs/glass/air structure by using Kretschmann geometry as functions of concentration of Au NPs in the liquid crystal, and the wavelength, polarization, and angle of incidence of the laser beam. We will discuss to what extent the results of these experiments support an interplay between the localized surface plasmon resonance at NPs/dielectric interfaces and optical propagation through the above-described structure.

  16. Dispersion relation and unphysical poles of Möbius domain-wall fermions in free field theory at finite Ls

    Science.gov (United States)

    Tomii, Masaaki

    2018-03-01

    We investigate the dispersion relation of Möbius domain-wall fermions in free field theory at finite Ls. We find that there are Ls - 1 extra poles of Möbius domain-wall fermions in addition to the pole which realizes the physical mode in the continuum limit. The unphysical contribution of these extra poles could be significant when we introduce heavy quarks. We show in this report the fundamental properties of these unphysical poles and discuss the optimal choice of Möbius parameters to minimize their contribution to four-dimensional physics.

  17. Dispersion relation and growth in a two-stream free electron laser with helical wiggler and ion channel guiding

    International Nuclear Information System (INIS)

    Mehdian, Hassan; Abbasi, Negar

    2008-01-01

    A linear theory of two-stream free electron laser (FEL) with helical wiggler and ion channel guiding is presented. The dispersion relation is obtained with the help of fluid theory and the growth rate is analyzed through the numerical solutions. The considerable enhancement of the growth rate is demonstrated due to the two-stream instability and continuous tuning of peak growth rate ratio, two-stream FEL compared to single-stream FEL, in terms of varying the ion channel frequency is illustrated

  18. Improved derivation of the modified BGK collision term and applications to the Hall effect and cold plasma dispersion relation

    International Nuclear Information System (INIS)

    Nagata, M.

    1983-01-01

    A derived addition to the BGK collision term,is improved and expressed in simple form. The collision frequency for scattering depends anisotropically on the velocity vector. The improved macroscopic equation of momentum flow is applied to the Hall effect, the cold plasma dispersion relation and the cyclotron resonance. The Hall coefficient which is constant in the case of the BGK collision term now depends on the magnetic field. It is also shown that, compared with the almost symmetric classical curves of cyclotron resonance, the new curves are considerably asymmetric and their half-widths are about 3/2 times the classical ones. (autho)

  19. Phonon dispersion relations in PrBa2Cu3O6+x (x≅0.2)

    International Nuclear Information System (INIS)

    Gardiner, C.H.; Boothroyd, A.T.; Larsen, B.H.; Reichardt, W.; Zhokhov, A.A.; Andersen, N.H.; Lister, S.J.S.; Wildes, A.R.

    2004-01-01

    We report measurements of the phonon dispersion relations in nonsuperconducting, oxygen-deficient PrBa 2 Cu 3 O 6+x (x≅0.2) by inelastic neutron scattering. The data are compared with a model of the lattice dynamics based on a common interatomic potential. Good agreement is achieved for all but two phonon branches, which are significantly softer than predicted. These modes are found to arise predominantly from motion of the oxygen ions in the CuO 2 planes. Analogous modes in YBa 2 Cu 3 O 6 are well described by the common interatomic potential model

  20. Realization of a complementary medium using dielectric photonic crystals.

    Science.gov (United States)

    Xu, Tao; Fang, Anan; Jia, Ziyuan; Ji, Liyu; Hang, Zhi Hong

    2017-12-01

    By exploiting the scaling invariance of photonic band diagrams, a complementary photonic crystal slab structure is realized by stacking two uniformly scaled double-zero-index dielectric photonic crystal slabs together. The space cancellation effect in complementary photonic crystals is demonstrated in both numerical simulations and microwave experiments. The refractive index dispersion of double-zero-index dielectric photonic crystal is experimentally measured. Using pure dielectrics, our photonic crystal structure will be an ideal platform to explore various intriguing properties related to a complementary medium.

  1. Reinvestigation of the dispersion relation of A{sub 1} phonon-polariton in LiNbO{sub 3} by the improved heterodyne ISRS study

    Energy Technology Data Exchange (ETDEWEB)

    Watanuki, Takeo; Yoshioka, Shinya; Kasahara, Masaru; Yagi, Toshirou [Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido (Japan); Crimmins, T.F.; Nelson, K.A. [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA (United States)

    2001-09-01

    The dispersion relation of the A{sub 1} phonon-polariton of ferroelectric LiNbO{sub 3} has been studied by the impulsive stimulated Raman scattering (ISRS) experiment improved with optical phase masks and heterodyne detection. A simple dispersion relation is revealed in contrast to the previous heterodyne ISRS study where several avoided crossing points were reported. The static dielectric constant obtained from the gradient of the dispersion curve with respect to the wave vector shows a good agreement with the previous dielectric measurement. (author)

  2. Reinvestigation of the Dispersion Relation of A1 Phonon-Polariton in LiNbO3 by the Improved Heterodyne ISRS Study

    Science.gov (United States)

    Watanuki, Takeo; Yoshioka, Shinya; Kasahara, Masaru; Crimmins, Timothy; Nelson, Keith; Yagi, Toshirou

    2001-09-01

    The dispersion relation of the A1 phonon-polariton of ferroelectric LiNbO3 has been studied by the impulsive stimulated Raman scattering (ISRS) experiment improved with optical phase masks and heterodyne detection. A simple dispersion relation is revealed in contrast to the previous heterodyne ISRS study where several avoided crossing points were reported. The static dielectric constant obtained from the gradient of the dispersion curve with respect to the wave vector shows a good agreement with the previous dielectric measurement.

  3. Quantifying the impact of relativity and of dispersion interactions on the activation of molecular oxygen promoted by noble metal nanoparticles

    KAUST Repository

    Kanoun, Mohammed

    2014-06-26

    We compared the mechanism of O2 dissociation catalyzed by Cu38, Ag38, and Au38 nanoparticles. Overall, our results indicate that O2 dissociation is extremely easy on Cu38, with an almost negligible barrier for the O-O breaking step. It presents an energy barrier close to 20 kcal/mol on Ag38, which decreases to slightly more than 10 kcal/mol on Au38. This behavior is analyzed to quantify the impact of relativity and of dispersion interactions through a comparison of nonrelativistic, scalar-relativistic, and dispersioncorrected DFT methods. Nonrelativistic calculations show a clear trend down the triad, with larger in size nanoparticle (NP), weaker O2 adsorption energy, and higher O2 dissociation barrier, which is so high for Au38 to be in sharp contrast with the mild conditions used experimentally. Inclusion of relativity has no impact on the O2 adsorption energy, but it reduces the energy barrier for O2 dissociation on Au38 from 30.1 to 11.4 kcal/mol, making it even lower than that on Ag38 and consistent with the mild conditions used experimentally. Dispersion interactions have a remarkable role in improving the adsorption ability of O2 on the heavier Ag38 and especially Au38 NPs, contributing roughly 50% of the total adsorption energy, while they have much less impact on O2 adsorption on Cu38.

  4. Microbial communities related to biodegradation of dispersed Macondo oil at low seawater temperature with Norwegian coastal seawater

    Science.gov (United States)

    Brakstad, Odd G; Throne-Holst, Mimmi; Netzer, Roman; Stoeckel, Donald M; Atlas, Ronald M

    2015-01-01

    The Deepwater Horizon (DWH) accident in 2010 created a deepwater plume of small oil droplets from a deepwater well in the Mississippi Canyon lease block 252 (‘Macondo oil’). A novel laboratory system was used in the current study to investigate biodegradation of Macondo oil dispersions (10 μm or 30 μm median droplet sizes) at low oil concentrations (2 mg l−1) in coastal Norwegian seawater at a temperature of 4–5°C. Whole metagenome analyses showed that oil biodegradation was associated with the successive increased abundances of Gammaproteobacteria, while Alphaproteobacteria (Pelagibacter) became dominant at the end of the experiment. Colwellia and Oceanospirillales were related to n-alkane biodegradation, while particularly Cycloclasticus and Marinobacter were associated with degradation of aromatic hydrocarbons (HCs). The larger oil droplet dispersions resulted in delayed sequential changes of Oceanospirillales and Cycloclasticus, related with slower degradation of alkanes and aromatic HCs. The bacterial successions associated with oil biodegradation showed both similarities and differences when compared with the results from DWH field samples and laboratory studies performed with deepwater from the Gulf of Mexico. PMID:26485443

  5. Relation between anchorings of liquid crystals and conformation changes in aligning agents by the Langmuir-Blodgett film technique investigation

    International Nuclear Information System (INIS)

    Zhu, Y.; Lu, Z.; Wei, Y.

    1995-01-01

    The anchoring direction of liquid crystals on a solid substrate surface depends upon many parameters characterizing the liquid-crystal--substrate interface, a variation of which may change this anchoring direction leading to the so-called anchoring transition. Here, based on the Langmuir-Blodgett film technique, we present two model systems to study the relation between anchoring directions and the conformation changes in aligning agents. A double-armed crown ether liquid crystal and a side chain polymer liquid crystal at an air-water interface both show phase transitions, accompanied by conformation changes. However, when the monolayers in different phases were transferred onto solid substrates to orient liquid crystals, we found that for the crown ether material the conformation change can alter the anchoring of liquid crystals between homeotropic and homogeneous alignments, while for the polymer liquid crystal, despite the conformation changes, the liquid crystals can only be aligned homeotropically. The involved mechanisms were briefly discussed in terms of the Landau-type phenomenological theory

  6. Distribution of vascular plant species in woodland patches of Ojców National Park (southern Poland in relation to seed dispersal

    Directory of Open Access Journals (Sweden)

    Łukasz Moszkowicz

    2016-03-01

    Full Text Available Plant diaspore dispersal is a fundamental process affecting the development of forest vegetation and its natural regeneration, especially with regard to typical woodland species, which spread slowly and form short-term soil seed banks. Most of these species have poor seed dispersal mechanisms, which is the major cause of their very slow expansion. The following questions were asked: (i is there a relationship between the age of a woodland and the presence of forest vascular plant species representing different seed dispersal types; (ii how do the proportions change between species representing different seed dispersal types in relation to the age of woodland; (iii what factors determine the presence of species representing a given seed dispersal type; (iv which factors affect the presence and which ones influence the abundance of selected woodland species? A multiple regression models were developed based on data obtained from 144 woodland patches designated for the study. A probit regression analysis was performed for selected species exhibiting various seed dispersal models. Woodland plants of all seed dispersal types show a significant relationship with the age of woodland, starting from the strongest linkage: anemochores, myrmecochores, endozoochores, epizoochores, barochores, autochores. As the woodland ages, the proportion of forest myrmecochores and anemochores grows, whilst the proportion of autochores, epizoochores and endozoochores shrinks. Results obtained indicate that the direct proximity of ancient woodland has a major effect on the occurrence of more poorly dispersing plants in recent woodlands, such as myrmecochores and heavy anemochores.

  7. Effect of Compression on the Molecular Arrangement of Itraconazole-Soluplus Solid Dispersions: Induction of Liquid Crystals or Exacerbation of Phase Separation?

    Science.gov (United States)

    Singh, Abhishek; Bharati, Avanish; Frederiks, Pauline; Verkinderen, Olivier; Goderis, Bart; Cardinaels, Ruth; Moldenaers, Paula; Van Humbeeck, Jan; Van den Mooter, Guy

    2016-06-06

    Predensification and compression are unit operations imperative to the manufacture of tablets and capsules. Such stress-inducing steps can cause destabilization of solid dispersions which can alter their molecular arrangement and ultimately affect dissolution rate and bioavailability. In this study, itraconazole-Soluplus solid dispersions with 50% (w/w) drug loading prepared by hot-melt extrusion (HME) were investigated. Compression was performed at both pharmaceutically relevant and extreme compression pressures and dwell times. The starting materials, powder, and compressed solid dispersions were analyzed using modulated differential scanning calorimetry (MDSC), X-ray diffraction (XRD), small- and wide-angle X-ray scattering (SWAXS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and broadband dielectric spectroscopy (BDS). MDSC analysis revealed that compression promotes phase separation of solid dispersions as indicated by an increase in glass transition width, occurrence of a peak in the nonreversing heat flow signal, and an increase in the net heat of fusion indicating crystallinity in the systems. SWAXS analysis ruled out the presence of mesophases. BDS measurements elucidated an increase in the Soluplus-rich regions of the solid dispersion upon compression. FTIR indicated changes in the spatiotemporal architecture of the solid dispersions mediated via disruption in hydrogen bonding and ultimately altered dynamics. These changes can have significant consequences on the final stability and performance of the solid dispersions.

  8. Dispersion engineering for integrated nanophotonics

    CERN Document Server

    Vanbésien, Olivier

    2014-01-01

    This book shows how dispersion engineering in two dimensional dielectric photonic crystals can provide new effects for the precise control of light propagation for integrated nanophotonics.Dispersion engineering in regular and graded photonic crystals to promote anomalous refraction effects is studied from the concepts to experimental demonstration via nanofabrication considerations. Self collimation, ultra and negative refraction, second harmonic generation, mirage and invisibility effects which lead to an unprecedented control of light propagation at the (sub-)wavelength scale for the

  9. High-pressure crystal chemistry of zircon, monazite, scheelite and related minerals

    International Nuclear Information System (INIS)

    Errandonea, D.

    2010-01-01

    Full text: Many crystal structures of ABO 4 compounds consists AO 8 bisdisphenoids and BO 4 tetrahedra. They include important mineral structures, e.g. zircon (ZrSiO 4 ), anhydrite (CaSO 4 ), silver perchlorate (AgClO 4 ), and scheelite (CaWO 4 ). These oxides, because of their compositional diversity and structural simplicity, played a key role in developing comparative crystal chemistry. In addition, zircon-type oxides exist in Nature being important minerals in the Earth mantle. Due to their incorporation of rare-earth (RE) elements they control the RE distribution in igneous rocks. Thus, the knowledge of their high-pressure (HP) structural behavior is relevant for mineral physics and chemistry (also for petrology). On the other hand, last decade RE phosphates and vanadates gained attention due to their optical and luminescent properties. Furthermore, given the crystal-chemical similarity between RE and actinides, phosphates were investigated for their use as solid-state repository for radioactive waste. The study of the HP mechanical and structural properties of ABO 4 oxides is relevant for all these subjects. In this presentation different HP pressure studies performed in zircon-, monazite-, and scheelite-type oxides and related minerals (e.g. wolframite, barite, and anhydrite) are reviewed. The studies include XRD, EXAFS, and Raman experiments using a diamond-anvil cell up to 50 GPa as well as ab initio calculations. The combination of the experiments and calculations reveals the existence of complex HP phase-diagrams. In particular, the occurrence of pressure-induced phase transitions is discussed in detail. The differential bond compressibility of different polyhedra is also commented and related to the anisotropic compressibility of the structures. Results for tungstates, molybdates, vanadates, phosphates, chromates, arsenates, silicates, and germanates are shown. Finally, a systematic for the HP structural sequence of the studied oxides is present and

  10. Nonlinear polarization rotation in a dispersion-flattened photonic-crystal fiber for ultrawideband (> 100 nm) all-optical wavelength conversion of 10 Gbit/s nonreturn-to-zero signals

    DEFF Research Database (Denmark)

    Kwok, C.H.; Chow, C.W.; Tsang, H.K.

    2006-01-01

    We study the conversion bandwidth of the cross-polarization-modulation (YPoIM)-based wavelength conversion scheme with a dispersion-flattened highly nonlinear photonic-crystal fiber for signals with a nonreturn-to-zero (NRZ) modulation format. Both theoretical and experimental results show...... that the conversion bandwidth can be extended to cover a very wide band, including S-, C-, and L-bands for 10 Gbit/s NRZ signals (a total bandwidth of 120 nm is experimentally demonstrated). We also study the theoretical bandwidth limit for 40 Gbit/s NRZ signals. A significant extension of the conversion bandwidth...

  11. Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

    OpenAIRE

    Yuriy Garbovskiy; Iryna Glushchenko

    2015-01-01

    The presence of ions in liquid crystals is one of the grand challenges that hinder the application of liquid crystals in various devices, which include advanced 3-D and flexible displays, tunable lenses, etc. Not only do they compromise the overall performance of liquid crystal devices, ions are also responsible for slow response, image sticking, and image flickering, as well as many other negative effects. Even highly purified liquid crystal materials can get contaminated during the manufact...

  12. Genetics of dispersal

    Science.gov (United States)

    Bocedi, Greta; Cote, Julien; Legrand, Delphine; Guillaume, Frédéric; Wheat, Christopher W.; Fronhofer, Emanuel A.; Garcia, Cristina; Henry, Roslyn; Husby, Arild; Baguette, Michel; Bonte, Dries; Coulon, Aurélie; Kokko, Hanna; Matthysen, Erik; Niitepõld, Kristjan; Nonaka, Etsuko; Stevens, Virginie M.; Travis, Justin M. J.; Donohue, Kathleen; Bullock, James M.; del Mar Delgado, Maria

    2017-01-01

    ABSTRACT Dispersal is a process of central importance for the ecological and evolutionary dynamics of populations and communities, because of its diverse consequences for gene flow and demography. It is subject to evolutionary change, which begs the question, what is the genetic basis of this potentially complex trait? To address this question, we (i) review the empirical literature on the genetic basis of dispersal, (ii) explore how theoretical investigations of the evolution of dispersal have represented the genetics of dispersal, and (iii) discuss how the genetic basis of dispersal influences theoretical predictions of the evolution of dispersal and potential consequences. Dispersal has a detectable genetic basis in many organisms, from bacteria to plants and animals. Generally, there is evidence for significant genetic variation for dispersal or dispersal‐related phenotypes or evidence for the micro‐evolution of dispersal in natural populations. Dispersal is typically the outcome of several interacting traits, and this complexity is reflected in its genetic architecture: while some genes of moderate to large effect can influence certain aspects of dispersal, dispersal traits are typically polygenic. Correlations among dispersal traits as well as between dispersal traits and other traits under selection are common, and the genetic basis of dispersal can be highly environment‐dependent. By contrast, models have historically considered a highly simplified genetic architecture of dispersal. It is only recently that models have started to consider multiple loci influencing dispersal, as well as non‐additive effects such as dominance and epistasis, showing that the genetic basis of dispersal can influence evolutionary rates and outcomes, especially under non‐equilibrium conditions. For example, the number of loci controlling dispersal can influence projected rates of dispersal evolution during range shifts and corresponding demographic impacts

  13. Gas-solute dispersivity ratio in granular porous media as related to particle size distribution and particle shape

    DEFF Research Database (Denmark)

    Pugliese, Lorenzo; Poulsen, Tjalfe; Straface, Salvatore

    2013-01-01

    Measurements of solute dispersion in porous media is generally much more time consuming than gas dispersion measurements performed under equivalent conditions. Significant time savings may therefore, be achieved if solute dispersion coefficients can be estimated based on measured gas dispersion...... data. This paper evaluates the possibility for estimating solute dispersion based on gas dispersion measurements. Breakthrough measurements were carried out at different fluid velocities (covering the same range in Reynolds number), using O2 and NaCl as gas and solute tracers, respectively. Three...... different, granular porous materials were used: (1) crushed granite (very angular particles), (2) gravel (particles of intermediate roundness) and (3) Leca® (almost spherical particles). For each material, 21 different particle size fractions were used. Gas and solute dispersion coefficients were determined...

  14. Switching VO2 Single Crystals and Related Phenomena: Sliding Domains and Crack Formation

    Directory of Open Access Journals (Sweden)

    Bertina Fisher

    2017-05-01

    Full Text Available VO2 is the prototype material for insulator–metal transition (IMT. Its transition at TIMT = 340 K is fast and consists of a large resistance jump (up to approximately five orders of magnitude, a large change in its optical properties in the visible range, and symmetry change from monoclinic to tetragonal (expansion by 1% along the tetragonal c-axis and 0.5% contraction in the perpendicular direction. It is a candidate for potential applications such as smart windows, fast optoelectronic switches, and field-effect transistors. The change in optical properties at the IMT allows distinguishing between the insulating and the metallic phases in the mixed state. Static or dynamic domain patterns in the mixed-state of self-heated single crystals during electric-field induced switching are in strong contrast with the percolative nature of the mixed state in switching VO2 films. The most impressive effect—so far unique to VO2—is the sliding of narrow semiconducting domains within a metallic background in the positive sense of the electric current. Here we show images from videos obtained using optical microscopy for sliding domains along VO2 needles and confirm a relation suggested in the past for their velocity. We also show images for the disturbing damage induced by the structural changes in switching VO2 crystals obtained for only a few current–voltage cycles.

  15. Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport in Low Gravity

    Science.gov (United States)

    Su, Ching-Hua; Ramachandran, N.

    2013-01-01

    Crystals of ZnSe and related ternary compounds, such as ZnSeS and ZnSeTe, will be grown by physical vapor transport in the Material Science Research Rack (MSRR) on International Space Station (ISS). The objective of the project is to determine the relative contributions of gravity-driven fluid flows to the compositional distribution, incorporation of impurities and defects, and deviation from stoichiometry observed in the crystals grown by vapor transport as results of buoyance-driven convection and growth interface fluctuations caused by irregular fluid-flows on Earth. The investigation consists of extensive ground-based experimental and theoretical research efforts and concurrent flight experimentation. The objectives of the ground-based studies are (1) obtain the experimental data and conduct the analyses required to define the optimum growth parameters for the flight experiments, (2) perfect various characterization techniques to establish the standard procedure for material characterization, (3) quantitatively establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low-gravity environment and (4) develop theoretical and analytical methods required for such evaluations. ZnSe and related ternary compounds have been grown by vapor transport technique with real time in-situ non-invasive monitoring techniques. The grown crystals have been characterized extensively by various techniques to correlate the grown crystal properties with the growth conditions.

  16. Ferroelectric BaTiO3 and LiNbO3 Nanoparticles Dispersed in Ferroelectric Liquid Crystal Mixtures: Electrooptic and Dielectric (Postprint)

    Science.gov (United States)

    2016-10-14

    KEYWORDS Ferroelectric liquid crystals; solid state ferroelectrics; FLC- nanocomposites ; surface phenomena Introduction Nematic Liquid Crystals are...FLC/ BaTiO3 nanocolloids were investigated. Similar results were obtained in [10] and [11] for FLC/BaTiO3 nanocomposites studied on non- harvested...polymer concentrations were spin coated at 3500 rpm for three minutes on the ITO coated glass plates to obtain films of different thick- ness

  17. Magnetic exciton dispersion in praseodymium

    DEFF Research Database (Denmark)

    Rainford, B. D.; Houmann, Jens Christian Gylden

    1971-01-01

    Measurements of the dispersion of magnetic excitons have been made in a single crystal of praseodymium metal using inelastic neutron scattering. A preliminary analysis of the data yields the first detailed information about the exchange interactions and the crystal field splittings in the light...

  18. STELLAR POPULATIONS ACROSS THE BLACK HOLE MASS–VELOCITY DISPERSION RELATION

    Energy Technology Data Exchange (ETDEWEB)

    Martín-Navarro, Ignacio; Brodie, Jean P.; Romanowsky, Aaron J. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Van den Bosch, Remco C. E. [Max-Planck Institut für Astronomie, Konigstuhl 17, D-69117 Heidelberg (Germany); Forbes, Duncan A., E-mail: imartinn@ucsc.edu [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia)

    2016-11-20

    Coevolution between supermassive black holes (BH) and their host galaxies is universally adopted in models for galaxy formation. In the absence of feedback from active galactic nuclei (AGNs), simulated massive galaxies keep forming stars in the local universe. From an observational point of view, however, such coevolution remains unclear. We present a stellar population analysis of galaxies with direct BH mass measurements and the BH mass– σ relation as a working framework. We find that over-massive BH galaxies, i.e., galaxies lying above the best-fitting BH mass– σ line, tend to be older and more α -element-enhanced than under-massive BH galaxies. The scatter in the BH mass– σ –[ α /Fe] plane is significantly lower than that in the standard BH mass– σ relation. We interpret this trend as an imprint of AGN feedback on the star formation histories of massive galaxies.

  19. Distribution of calcium oxalate crystals in floral organs of Araceae in relation to pollination strategy.

    Science.gov (United States)

    Coté, Gary G; Gibernau, Marc

    2012-07-01

    Many flowers are pollinated by potentially hungry insects, yet flowers also contain gametes and embryos which must be protected from predation. Microscopic calcium oxalate crystals in plant tissues have been proposed to protect against herbivory. Aroids, which have an unusual diversity of such crystals, also exhibit diverse pollination strategies. Many species have pollinators that do not feed while visiting the flowers, while other species, especially those pollinated by beetles, offer sterile staminodia as food rewards. We examined flowers of 21 aroid species with various pollination strategies to test the hypothesis that crystals protect vital gametes and embryos while allowing consumption of food bribes. Aroid inflorescences collected from the field or from greenhouse material were sectioned, cleared, and examined by bright field and polarization microscopy. All species examined, regardless of pollination strategy, arrayed crystals around unshed pollen and ovules. Less vital tissues, such as odoriferous appendages, had few crystals. Staminodia offered as food to beetle pollinators, however, differed greatly between species in their crystal contents. Some had minimal crystals; some had crystals in patterns suggesting they limit beetle feeding; still others had abundant crystals in no obvious pattern. The results are consistent with crystals protecting against insect predation of gametes and embryos. However, the role of crystals in food-bribe staminodia is unclear. They may limit and direct feeding by beetles in some species, while in others they might have no protective role.

  20. Trapped Bose-Einstein condensates with Planck-scale induced deformation of the energy-momentum dispersion relation

    International Nuclear Information System (INIS)

    Briscese, F.

    2012-01-01

    We show that harmonically trapped Bose-Einstein condensates can be used to constrain Planck-scale physics. In particular we prove that a Planck-scale induced deformation of the Minkowski energy-momentum dispersion relation δE≃ξ 1 mcp/2M p produces a shift in the condensation temperature T c of about ΔT c /T c 0 ≃10 -6 ξ 1 for typical laboratory conditions. Such a shift allows to bound the deformation parameter up to |ξ 1 |≤10 4 . Moreover we show that it is possible to enlarge ΔT c /T c 0 and improve the bound on ξ 1 lowering the frequency of the harmonic trap. Finally we compare the Planck-scale induced shift in T c with similar effects due to interboson interactions and finite size effects.

  1. Unified description of the neutron-/sup 208/Pb mean field between -20 and +165 MeV from the dispersion relation constraint

    International Nuclear Information System (INIS)

    Johnson, C.H.; Horen, D.J.; Mahaux, C.

    1987-01-01

    The real part of the central neutron-/sup 208/Pb mean field is the sum of a Hartree-Fock component plus a dispersive component. In keeping with theoretical expectations, the Hartree-Fock field is assumed to have a Woods-Saxon shape whose depth decreases exponentially with increasing energy and whose radius and diffuseness are independent of energy. The dispersive component is determined from the imaginary part of the optical-model potential by making use of the dispersion relation which connects these two quantities. The imaginary part is written as the sum of a volume and a surface-peaked contribution. The dispersion relation then implies that the real dispersive contribution is also the sum of volume and surface-peaked components. The parameters of the complex mean field are determined by fitting the available differential and polarization cross sections in the energy domain [4, 40 MeV] and the total cross sections in the domain [1,120 MeV]; these data are contained in previous published or unpublished reports, but new measurements of the total cross sections are presented from 1 to 25 MeV. Good fits to these cross sections, and also to unpublished total cross sections for energies up to 165 MeV, are obtained despite the fact that the number of adjusted parameters is quite small because of our use of the constraint implied by the dispersion relation

  2. The variability of processes involved in transgene dispersal - case studies from Brassica and related genera

    DEFF Research Database (Denmark)

    Bagger Jørgensen, Rikke; Hauser, Thure Pavlo; D'Hertefeldt, T.

    2009-01-01

    Background, aim, and scope We strive to predict consequences of genetically modified plants (GMPs) being cultivated openly in the environment, as human and animal health, biodiversity, agricultural practise and farmers’ economy could be affected. Therefore, it is unfortunate that the risk...... is a valuable tool in identifying key factors in the gene-flow process for which more knowledge is needed, and identifying parameters and processes which are relatively insensitive to change and therefore require less attention in future collections of data. But the interdependence between models...

  3. Application of energy dispersive XRF-spectrometry to analyse nutritional elements in relation to cancer

    International Nuclear Information System (INIS)

    Hota, P.K.; Vijayan, V.; Singh, L.P.

    2001-01-01

    Food is the principal media for intake of elements from environment to human body. Thus, it is felt important to determine the daily dietary intake of such elements in the field of toxicity and nutrition, the deficiency or sufficiency of which may lead to various diseases, disorders and allergies in human health. In this study, the elements present in commonly used cereals, pulses, noodles, some condiments/spices, tobacco products, some common leaves used in herbal medicine and tea leaves have been analyzed using EDXRF spectrometry technique. Elemental concentrations of K, Ca, Fe, Sr, Mn, Zn, Cu, Pb, As and Se are detected and quantified in all the samples using this method. The results are discussed in relation to cancer. (author)

  4. Anomalous magnetoresistance effect in sputtered TbFeCo relating to dispersed magnetic moment

    International Nuclear Information System (INIS)

    Yumoto, S.; Toki, K.; Okada, O.; Gokan, H.

    1988-01-01

    The electric resistance is sputtered TbFeCo has been measured at room temperature as a function of magnetic field perpendicular to the film plane. Two kinds of anomalous magnetoresistance have been observed. One is a magnetoresistance peak in the magnetization reversal region. The other is reversible change proportional to the applied magnetic field, appearing in the other region. The magnetoresistance peak agrees well with a curve calculated from experimental Hall loop, using a phenomenological relation between anomalous magnetoresistance and anomalous Hall voltage. The magnetoresistance peak is found to originate from magnetic domain walls. The linear magnetoresistance change for TM dominant samples appears in a direction opposite to that for RE dominant samples. The linear change can't be derived from Hall loop

  5. Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

    Directory of Open Access Journals (Sweden)

    Yuriy Garbovskiy

    2015-11-01

    Full Text Available The presence of ions in liquid crystals is one of the grand challenges that hinder the application of liquid crystals in various devices, which include advanced 3-D and flexible displays, tunable lenses, etc. Not only do they compromise the overall performance of liquid crystal devices, ions are also responsible for slow response, image sticking, and image flickering, as well as many other negative effects. Even highly purified liquid crystal materials can get contaminated during the manufacturing process. Moreover, liquid crystals can degrade over time and generate ions. All of these factors raise the bar for their quality control, and increase the manufacturing cost of liquid crystal products. A decade of dedicated research has paved the way to the solution of the issues mentioned above through merging liquid crystals and nanotechnology. Nano-objects (guests that are embedded in the liquid crystals (hosts can trap ions, which decreases the ion concentration and electrical conductivity, and improves the electro-optical response of the host. In this paper, we (i review recently published works reporting the effects of nanoscale dopants on the electrical properties of liquid crystals; and (ii identify the most promising inorganic and organic nanomaterials suitable to capture ions in liquid crystals.

  6. Relative contribution of dispersal and natural selection to the maintenance of a hybrid zone in Littorina.

    Science.gov (United States)

    Cruz, Raquel; Vilas, Carlos; Mosquera, Javier; García, Carlos

    2004-12-01

    Habitat preference behavior may play an important role in nonallopatric speciation. However, most examples of habitat preference contributing to differentiation within natural populations correspond to parasites or herbivores living in the discrete environments constituted by their animal or plant hosts. In the present study we investigated migration guided by habitat preference in the intertidal snail Littorina saxatilis in a hybrid zone associated with an ecotone across the shore, which is therefore a continuously varying environment. First, we found evidence for this behavior in one of the two locations studied. Second, we made reciprocal transplants to suppress the phenotypic gradient observed across the hybrid zone and measured the relative contributions of selection and migration to its regeneration. Selection played an important role at the two locations studied, but migration was only important at one, where it accounted for between a third and a half of the regenerated gradient. This overall minor effect of migration was relevant for theoretical models dealing with nonallopatric speciation, because it suggested that variation for habitat preference did not have an important role in the initiation of the differentiation process. The preference behavior observed in the hybrid zone would have evolved secondarily, as a consequence of habitat-dependent fitness differences between phenotypes.

  7. Average and dispersion of the luminosity-redshift relation in the concordance model

    CERN Document Server

    Ben-Dayan, I.; Marozzi, G.; Nugier, F.; Veneziano, G.

    2013-01-01

    Starting from the luminosity-redshift relation recently given up to second order in the Poisson gauge, we calculate the effects of the realistic stochastic background of perturbations of the so-called concordance model on the combined light-cone and ensemble average of various functions of the luminosity distance, and on their variance, as functions of redshift. We apply a gauge-invariant light-cone averaging prescription which is free from infrared and ultraviolet divergences, making our results robust with respect to changes of the corresponding cutoffs. Our main conclusions, in part already anticipated in a recent letter for the case of a perturbation spectrum computed in the linear regime, are that such inhomogeneities not only cannot avoid the need for dark energy, but also cannot prevent, in principle, the determination of its parameters down to an accuracy of order $10^{-3}-10^{-5}$, depending on the averaged observable and on the regime considered for the power spectrum. However, taking into account t...

  8. Axonal transmission in the retina introduces a small dispersion of relative timing in the ganglion cell population response.

    Directory of Open Access Journals (Sweden)

    Günther Zeck

    Full Text Available BACKGROUND: Visual stimuli elicit action potentials in tens of different retinal ganglion cells. Each ganglion cell type responds with a different latency to a given stimulus, thus transforming the high-dimensional input into a temporal neural code. The timing of the first spikes between different retinal projection neurons cells may further change along axonal transmission. The purpose of this study is to investigate if intraretinal conduction velocity leads to a synchronization or dispersion of the population signal leaving the eye. METHODOLOGY/PRINCIPAL FINDINGS: We 'imaged' the initiation and transmission of light-evoked action potentials along individual axons in the rabbit retina at micron-scale resolution using a high-density multi-transistor array. We measured unimodal conduction velocity distributions (1.3±0.3 m/sec, mean ± SD for axonal populations at all retinal eccentricities with the exception of the central part that contains myelinated axons. The velocity variance within each piece of retina is caused by ganglion cell types that show narrower and slightly different average velocity tuning. Ganglion cells of the same type respond with similar latency to spatially homogenous stimuli and conduct with similar velocity. For ganglion cells of different type intraretinal conduction velocity and response latency to flashed stimuli are negatively correlated, indicating that differences in first spike timing increase (up to 10 msec. Similarly, the analysis of pair-wise correlated activity in response to white-noise stimuli reveals that conduction velocity and response latency are negatively correlated. CONCLUSION/SIGNIFICANCE: Intraretinal conduction does not change the relative spike timing between ganglion cells of the same type but increases spike timing differences among ganglion cells of different type. The fastest retinal ganglion cells therefore act as indicators of new stimuli for postsynaptic neurons. The intraretinal dispersion

  9. Chemical Analysis of Reaction Rims on Olivine Crystals in Natural Samples of Black Dacite Using Energy-Dispersive X-Ray Spectroscopy, Lassen Peak, CA.

    Science.gov (United States)

    Graham, N. A.

    2014-12-01

    Lassen Volcanic Center is the southernmost volcanic region in the Cascade volcanic arc formed by the Cascadia Subduction Zone. Lassen Peak last erupted in 1915 in an arc related event producing a black dacite material containing xenocrystic olivine grains with apparent orthopyroxene reaction rims. The reaction rims on these olivine grains are believed to have formed by reactions that ensued from a mixing/mingling event that occurred prior to eruption between the admixed mafic andesitic magma and a silicic dacite host material. Natural samples of the 1915 black dacite from Lassen Peak, CA were prepared into 15 polished thin sections and carbon coated for analysis using a FEI Quanta 250 Scanning Electron Microscope (SEM) to identify and measure mineral textures and disequilibrium reaction rims. Observed mineralogical textures related to magma mixing include biotite and amphibole grains with apparent dehydration/breakdown rims, pyroxene-rimmed quartz grains, high concentration of microlites in glass matrix, and pyroxene/amphibole reaction rims on olivine grains. Olivine dissolution is evidenced as increased iron concentration toward convolute edges of olivine grains as observed by Backscatter Electron (BSE) imagery and elemental mapping using NSS spectral imaging software. In an attempt to quantify the area of reaction rim growth on olivine grains within these samples, high-resolution BSE images of 30 different olivine grains were collected along with Energy-Dispersive X-Ray Spectroscopy (EDS) of different phases. Olivine cores and rims were extracted from BSE images using Photoshop and saved as separate image files. ImageJ software was used to calculate the area (μm2) of the core and rim of these grains. Average pyroxene reaction rim width for 30 grains was determined to be 11.68+/-1.65 μm. Rim widths of all 30 grains were averaged together to produce an overall average rim width for the Lassen Peak black dacite. By quantifying the reaction rims on olivine grains

  10. A chemical signal possibly related to physiology in fossil cells detected by energy dispersive X-ray microanalysis.

    Science.gov (United States)

    Wang, X

    2006-02-01

    Energy dispersive X-ray microanalysis (EDXMA) is a widely used tool employed to detect elemental composition and its spatial distribution in a sample without causing damage. Charcoalified cytoplasm is a new type of fossil material that came to people's attention only recently. In this paper, EDXMA is used for the first time to detect the spatial elemental distribution in charcoalified cytoplasm of two fossil plants that are more than 100 million years old. The results demonstrate certain elemental distribution patterns within charcoalified cytoplasm and the surrounding cell walls. Based on the results from cytological studies of extant material, the heterogeneous spatial elemental distribution within the charcoalified cytoplasm has the potential to be related to the maturation of cells, the presence of certain organelles, and the physiology of these organelles. This is the first chemical signal detected in cytoplasm residue that can possibly be related to plant physiology. This paves the way for further research on fossil cytoplasm, which will better our understanding on the physiology of fossil plants.

  11. Dispersion of γ-Alumina Nano-Sized Spherical Particles in a Calamitic Liquid Crystal. Study and Optimization of the Confinement Effects

    Science.gov (United States)

    Diez-Berart, Sergio; López, David O.; Sebastián, Nerea; de la Fuente, María Rosario; Salud, Josep; Robles-Hernández, Beatriz; Pérez-Jubindo, Miguel Ángel

    2014-01-01

    We report an experimental study on confined systems formed by butyloxybenzylidene octylaniline liquid crystal (4O.8) + γ-alumina nanoparticles. The effects of the confinement in the thermal and dielectric properties of the liquid crystal under different densities of nanoparticles is analyzed by means of high resolution Modulated Differential Scanning Calorimetry (MDSC) and broadband dielectric spectroscopy. First, a drastic depression of the N-I and SmA-N transition temperatures is observed with confinement, the more concentration of nanoparticles the deeper this depression is, driving the nematic range closer to the room temperature. An interesting experimental law is found for both transition temperatures. Second, the change in shape of the heat capacity peaks is quantified by means of the full width half maximum (FWHM). Third, the confinement does not noticeably affect the molecular dynamics. Finally, the combination of nanoparticles and the external applied electric field tends to favor the alignment of the molecules in metallic cells. All these results indicate that the confinement of liquid crystals by means of γ-alumina nanoparticles could be optimum for liquid crystal-based electrooptic devices. PMID:28788528

  12. Giant magnon solution and dispersion relation in string theory in AdS3×S3×T4 with mixed flux

    International Nuclear Information System (INIS)

    Hoare, B.; Stepanchuk, A.; Tseytlin, A.A.

    2014-01-01

    We address the question of the exact form of the dispersion relation for light-cone string excitations in string theory in AdS 3 ×S 3 ×T 4 with mixed R–R and NS–NS 3-form fluxes. The analogy with string theory in AdS 5 ×S 5 suggests that in addition to the data provided by the perturbative near-BMN expansion and symmetry algebra considerations there is another source of information for the dispersion relation – the semiclassical giant magnon solution. In earlier work in (arXiv:1303.1037) and (arXiv:1304.4099) we found that the symmetry algebra constraints, which are consistent with a perturbative expansion, do not completely determine the form of the dispersion relation. The aim of the present paper is to fix the dispersion relation by constructing a generalisation of the known dyonic giant magnon soliton on S 3 to the presence of a non-zero NS–NS flux described by a WZ term in the string action (with coefficient q). We find that the angular momentum of this soliton gets shifted by a term linear in world-sheet momentum p. We also discuss the symmetry algebra of the string light-cone S-matrix and show that the exact dispersion relation, which should have the correct perturbative BMN and semiclassical giant magnon limits, should also contain such a linear momentum term. The simplicity of the resulting bound-state picture provides a strong argument in favour of this dispersion relation

  13. The crystal chemistry of inorganic metal borohydrides and their relation to metal oxides.

    Science.gov (United States)

    Černý, Radovan; Schouwink, Pascal

    2015-12-01

    The crystal structures of inorganic homoleptic metal borohydrides are analysed with respect to their structural prototypes found amongst metal oxides in the inorganic databases such as Pearson's Crystal Data [Villars & Cenzual (2015). Pearson's Crystal Data. Crystal Structure Database for Inorganic Compounds, Release 2014/2015, ASM International, Materials Park, Ohio, USA]. The coordination polyhedra around the cations and the borohydride anion are determined, and constitute the basis of the structural systematics underlying metal borohydride chemistry in various frameworks and variants of ionic packing, including complex anions and the packing of neutral molecules in the crystal. Underlying nets are determined by topology analysis using the program TOPOS [Blatov (2006). IUCr CompComm. Newsl. 7, 4-38]. It is found that the Pauling rules for ionic crystals apply to all non-molecular borohydride crystal structures, and that the latter can often be derived by simple deformation of the close-packed anionic lattices c.c.p. and h.c.p., by partially removing anions and filling tetrahedral or octahedral sites. The deviation from an ideal close packing is facilitated in metal borohydrides with respect to the oxide due to geometrical and electronic considerations of the BH4(-) anion (tetrahedral shape, polarizability). This review on crystal chemistry of borohydrides and their similarity to oxides is a contribution which should serve materials engineers as a roadmap to design new materials, synthetic chemists in their search for promising compounds to be prepared, and materials scientists in understanding the properties of novel materials.

  14. Hydrogen-related complexes in Li-diffused ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Corolewski, Caleb D. [Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164-2814 (United States); Parmar, Narendra S.; Lynn, Kelvin G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2814 (United States); McCluskey, Matthew D., E-mail: mattmcc@wsu.edu [Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164-2814 (United States); Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States)

    2016-07-21

    Zinc oxide (ZnO) is a wide band gap semiconductor and a potential candidate for next generation white solid state lighting applications. In this work, hydrogen-related complexes in lithium diffused ZnO single crystals were studied. In addition to the well-known Li-OH complex, several other hydrogen defects were observed. When a mixture of Li{sub 2}O and ZnO is used as the dopant source, zinc vacancies are suppressed and the bulk Li concentration is very high (>10{sup 19 }cm{sup −3}). In that case, the predominant hydrogen complex has a vibrational frequency of 3677 cm{sup −1}, attributed to surface O-H species. When Li{sub 2}CO{sub 3} is used, a structured blue luminescence band and O-H mode at 3327 cm{sup −1} are observed at 10 K. These observations, along with positron annihilation measurements, suggest a zinc vacancy–hydrogen complex, with an acceptor level ∼0.3 eV above the valence-band maximum. This relatively shallow acceptor could be beneficial for p-type ZnO.

  15. Crystal-Clear Technology.

    Science.gov (United States)

    Ondris-Crawford, Renate J.; And Others

    1993-01-01

    Provides diagrams to aid in discussing polymer dispersed liquid crystal (PDLC) technology. Equipped with a knowledge of PDLC, teachers can provide students with insight on how the gap between basic science and technology is bridged. (ZWH)

  16. Dispersion relation for space-charge waves in a warm plasma-filled elliptical waveguide in an infinite axial magnetic field

    Science.gov (United States)

    Abdoli-Arani, A.; Safari, S.

    2015-04-01

    A perfectly conducting elliptical cylinder filled with a warm plasma and immersed in an infinite axial magnetic field is considered. Using Maxwell's equations and dielectric tensor, a Mathieu differential equation for axial component of electric field is obtained. Considering the boundary conditions, dispersion relation for waves in a plasma of warm electrons and immobile ions, which fills an elliptical waveguide and it is under the action of infinite axial magnetic field are calculated. Furthermore, dispersion relation and scalar potential in the quasi-static approximation in a cold magnetized plasma elliptical waveguide is calculated. The obtained results are graphically presented.

  17. Dispersion of traffic-related exhaust particles near the Berlin urban motorway – estimation of fleet emission factors

    Directory of Open Access Journals (Sweden)

    W. Birmili

    2009-04-01

    Full Text Available Atmospheric particle number size distributions of airborne particles (diameter range 10–500 nm were collected over ten weeks at three sites in the vicinity of the A100 urban motorway in Berlin, Germany. The A100 carries about 180 000 vehicles on a weekday. The roadside particle distributions showed a number maximum between 20 and 60 nm clearly related to the motorway emissions. The average total number concentration at roadside was 28 000 cm−3 with a total range of 1200–168 000 cm−3. At distances of 80 and 400 m from the motorway the concentrations decreased to mean levels of 11 000 and 9000 cm−3, respectively. An obstacle-resolving dispersion model was applied to simulate the 3-D flow field and traffic tracer transport in the urban environment around the motorway. By inverse modelling, vehicle emission factors were derived that are representative of a fleet with a relative share of 6% lorry-like vehicles, and driving at a speed of 80 km h−1. Three different calculation approaches were compared, which differ in the choice of the experimental winds driving the flow simulation. The average emission factor per vehicle was 2.1 (±0.2 · 1014 km−1 for particle number and 0.077 (±0.01 · 1014 cm3 km−1 for particle volume. Regression analysis suggested that lorry-like vehicles emit 123 (±28 times more particle number than passenger car-like vehicles, and lorry-like vehicles account for about 91% of particulate number emissions on weekdays. Our work highlights the increasing applicability of 3-D flow models in urban microscale environments and their usefulness for determining traffic emission factors.

  18. Surface polarity of beta-HMX crystal and the related adhesive forces with Estane binder.

    Science.gov (United States)

    Yang, Lu

    2008-12-02

    Here I present the results on the study of surface properties of beta-HMX crystal utilizing molecular dynamics simulations. The surface polarity of three principal crystal surfaces, (011), (010), and (110), is investigated by measuring the water contact angles. The calculated contact angles are in excellent agreement with the values measured by experiment and show that the surface polarity of three crystal surfaces are different. The free energies and forces of detaching an Estane chain (with and without surrounding nitroplasticizer molecules) from the three principal crystal surfaces are also calculated using the umbrella sampling method. I find that the force for Estane detachment increases with the increasing HMX surface polarity. In addition, my results show that the nitroplasticizer also plays an important role in the adhesion between Estane and HMX surfaces.

  19. Nano and micro reoriented domains and their relation with the crystal structure in the new ferroelectric boracite Zn3B7O13Br

    Science.gov (United States)

    Campa-Molina, J.; Ulloa-Godínez, S.; Barrera, A.; Bucio, L.; Mata, J.

    2006-05-01

    A new zinc brome boracite Zn3B7O13Br has been grown by a chemical transport reaction in closed quartz ampoules at 920 K. The crystal structure was characterized by Rietveld refinement. Ferroelectric nano and micro reorientable domains were found in this material using polarizing optical microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Chemical analysis was performed with x-ray energy dispersive spectroscopy (EDX). In the crystal, a new structure transition at 586 K from orthorhombic (Pca 21) to cubic cell (F\\overline 4 3c ) has been found. This transition was corroborated by differential scanning calorimetry (DSC).

  20. Agglomerate properties and dispersibility changes of salmeterol xinafoate from powders for inhalation after storage at high relative humidity.

    Science.gov (United States)

    Das, Shyamal; Larson, Ian; Young, Paul; Stewart, Peter

    2009-06-28

    This study investigated changes in agglomeration and the mechanism of dispersibility decrease of salmeterol xinafoate (SX) from SX-lactose mixtures for inhalation after storage at 75% RH for 3 months. The dispersibility, PSD and in situ PSD of aerosol plumes of SX alone and SX-coarse lactose (CL) mixtures containing 0, 5, 10 and 20% micronized lactose (ML) before and after storage were determined by a Next Generation Impactor (NGI), a Mastersizer 2000 and a Spraytec, respectively. The PSD of ML increased after storage at 75% RH, but dispersibility of SX using the stored ML increased. After storage, the %SX of the mixture containing 20% ML (M20F) significantly increased (Pagglomerates, probably occurring through enhanced capillary interaction and/or solid bridging of ML, entrapping and preventing the release of SX particles.

  1. Hydrodynamic disperser

    Energy Technology Data Exchange (ETDEWEB)

    Bulatov, A.I.; Chernov, V.S.; Prokopov, L.I.; Proselkov, Yu.M.; Tikhonov, Yu.P.

    1980-01-15

    A hydrodynamic disperser is suggested which contains a housing, slit nozzles installed on a circular base arranged opposite from each other, resonators secured opposite the nozzle and outlet sleeve. In order to improve the effectiveness of dispersion by throttling the flow, each resonator is made in the form of a crimped plate with crimpings that decrease in height in a direction towards the nozzle.

  2. Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF)

    Science.gov (United States)

    Kevin T. Smith; Jean Christophe Balouet; Walter C. Shortle; Michel Chalot; François Beaujard; Hakan Grudd; Don A. Vroblesky; Joel G. Burken

    2014-01-01

    Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to...

  3. Hydrodynamic dispersion

    International Nuclear Information System (INIS)

    Pryce, M.H.L.

    1985-01-01

    A dominant mechanism contributing to hydrodynamic dispersion in fluid flow through rocks is variation of travel speeds within the channels carrying the fluid, whether these be interstices between grains, in granular rocks, or cracks in fractured crystalline rocks. The complex interconnections of the channels ensure a mixing of those parts of the fluid which travel more slowly and those which travel faster. On a macroscopic scale this can be treated statistically in terms of the distribution of times taken by a particle of fluid to move from one surface of constant hydraulic potential to another, lower, potential. The distributions in the individual channels are such that very long travel times make a very important contribution. Indeed, while the mean travel time is related to distance by a well-defined transport speed, the mean square is effectively infinite. This results in an asymmetrical plume which differs markedly from a gaussian shape. The distribution of microscopic travel times is related to the distribution of apertures in the interstices, or in the microcracks, which in turn are affected in a complex way by the stresses acting on the rock matrix

  4. Evaluation of regional and local atmospheric dispersion models for the analysis of traffic-related air pollution in urban areas

    Science.gov (United States)

    Fallah-Shorshani, Masoud; Shekarrizfard, Maryam; Hatzopoulou, Marianne

    2017-10-01

    Dispersion of road transport emissions in urban metropolitan areas is typically simulated using Gaussian models that ignore the turbulence and drag induced by buildings, which are especially relevant for areas with dense downtown cores. To consider the effect of buildings, street canyon models are used but often at the level of single urban corridors and small road networks. In this paper, we compare and validate two dispersion models with widely varying algorithms, across a modelling domain consisting of the City of Montreal, Canada accounting for emissions of more 40,000 roads. The first dispersion model is based on flow decomposition into the urban canopy sub-flow as well as overlying airflow. It takes into account the specific height and geometry of buildings along each road. The second model is a Gaussian puff dispersion model, which handles complex terrain and incorporates three-dimensional meteorology, but accounts for buildings only through variations in the initial vertical mixing coefficient. Validation against surface observations indicated that both models under-predicted measured concentrations. Average weekly exposure surfaces derived from both models were found to be reasonably correlated (r = 0.8) although the Gaussian dispersion model tended to underestimate concentrations around the roadways compared to the street canyon model. In addition, both models were used to estimate exposures of a representative sample of the Montreal population composed of 1319 individuals. Large differences were noted whereby exposures derived from the Gaussian puff model were significantly lower than exposures derived from the street canyon model, an expected result considering the concentration of population around roadways. These differences have large implications for the analyses of health effects associated with NO2 exposure.

  5. Nucleation of polypropylene crystallization with gold nanoparticles. Part 2: relation between particle morphology and nucleation activity

    Czech Academy of Sciences Publication Activity Database

    Šlouf, Miroslav; Vacková, Taťana; Zhigunov, Alexander; Sikora, Antonín; Piorkowska, E.

    2016-01-01

    Roč. 55, č. 4 (2016), s. 393-410 ISSN 0022-2348 R&D Projects: GA ČR GAP205/10/0348; GA ČR(CZ) GA14-17921S Institutional support: RVO:61389013 Keywords : crystallization * gold nanoparticles * isotactic polyproplylene Subject RIV: JJ - Other Materials Impact factor: 0.828, year: 2016

  6. Demand for Substance Abuse Treatment Related to Use of Crystal Methamphetamine in Ontario: An Observational Study

    Science.gov (United States)

    Brands, Bruna; Corea, Larry; Strike, Carol; Singh, Veeran-Anne S.; Behrooz, Renee C.; Rush, Brian

    2012-01-01

    Concerns about methamphetamine/crystal methamphetamine (MA) have featured prominently in the Canadian media and on addiction treatment agency agendas. We examined MA admissions at addiction treatment agencies to determine if a service gap existed. In 2006, all addiction treatment agencies (n = 124) in Ontario, Canada were invited to complete an…

  7. Crystal structure of fervidolysin from Fervidobacterium pennivorans, a keratinolytic enzyme related to subtilisin

    NARCIS (Netherlands)

    Kim, J.S.; Kluskens, L.D.; Vos, de W.M.; Huber, R.; Oost, van der J.

    2004-01-01

    Structure-forming fibrous proteins like keratins, gelatins and collagens are degraded only by a few proteases as their tight packing limits access to the potential cleavage sites. To understand the keratin degradation in detail, we describe the first crystal structure of a keratin-degrading enzyme

  8. Large-bandwidth planar photonic crystal waveguides

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Lavrinenko, Andrei

    2002-01-01

    A general design principle is presented for making finite-height photonic crystal waveguides that support leakage-free guidance of light over large frequency intervals. The large bandwidth waveguides are designed by introducing line defects in photonic crystal slabs, where the material in the line...... defect has appropriate dispersion properties relative to the photonic crystal slab material surrounding the line defect. A three-dimensional theoretical analysis is given for large-bandwidth waveguide designs based on a silicon-air photonic crystal slab suspended in air. In one example, the leakage......-free single-mode guidance is found for a large frequency interval covering 60% of the photonic band-gap....

  9. Effects of canyon geometry on the distribution of traffic-related air pollution in a large urban area: Implications of a multi-canyon air pollution dispersion model

    Science.gov (United States)

    Fu, Xiangwen; Liu, Junfeng; Ban-Weiss, George A.; Zhang, Jiachen; Huang, Xin; Ouyang, Bin; Popoola, Olalekan; Tao, Shu

    2017-09-01

    Street canyons are ubiquitous in urban areas. Traffic-related air pollutants in street canyons can adversely affect human health. In this study, an urban-scale traffic pollution dispersion model is developed considering street distribution, canyon geometry, background meteorology, traffic assignment, traffic emissions and air pollutant dispersion. In the model, vehicle exhausts generated from traffic flows first disperse inside street canyons along the micro-scale wind field generated by computational fluid dynamics (CFD) model. Then, pollutants leave the street canyon and further disperse over the urban area. On the basis of this model, the effects of canyon geometry on the distribution of NOx and CO from traffic emissions were studied over the center of Beijing. We found that an increase in building height leads to heavier pollution inside canyons and lower pollution outside canyons at pedestrian level, resulting in higher domain-averaged concentrations over the area. In addition, canyons with highly even or highly uneven building heights on each side of the street tend to lower the urban-scale air pollution concentrations at pedestrian level. Further, increasing street widths tends to lead to lower pollutant concentrations by reducing emissions and enhancing ventilation simultaneously. Our results indicate that canyon geometry strongly influences human exposure to traffic pollutants in the populated urban area. Carefully planning street layout and canyon geometry while considering traffic demand as well as local weather patterns may significantly reduce inhalation of unhealthy air by urban residents.

  10. Relations de Dispersion et Diffusion des Glueballs et des Mesons dans la Theorie de Jauge U(1)(2+1) Compacte

    Science.gov (United States)

    Ahmed, Chaara El Mouez

    Nous avons etudie les relations de dispersion et la diffusion des glueballs et des mesons dans le modele U(1)_{2+1} compact. Ce modele a ete souvent utilise comme un simple modele de la chromodynamique quantique (QCD), parce qu'il possede le confinement ainsi que les etats de glueballs. Par contre, sa structure mathematique est beaucoup plus simple que la QCD. Notre methode consiste a diagonaliser l'Hamiltonien de ce modele dans une base appropriee de graphes et sur reseau impulsion, afin de generer les relations de dispersion des glueballs et des mesons. Pour la diffusion, nous avons utilise la methode dependante du temps pour calculer la matrice S et la section efficace de diffusion des glueballs et des mesons. Les divers resultats obtenus semblent etre en accord avec les travaux anterieurs de Hakim, Alessandrini et al., Irving et al., qui eux, utilisent plutot la theorie des perturbations en couplage fort, et travaillent sur un reseau espace-temps.

  11. Nanoparticle guests in lyotropic liquid crystals

    Science.gov (United States)

    Dölle, Sarah; Park, Ji Hyun; Schymura, Stefan; Jo, Hyeran; Scalia, Giusy; Lagerwall, Jan P. F.

    In this chapter we discuss the benefits, peculiarities and main challenges related to nanoparticle templating in lyotropic liquid crystals. We first give a brief bird's-eye view of the field, discussing different nanoparticles as well as different lyotropic hosts that have been explored, but then quickly focus on the dispersion of carbon nanotubes in surfactant-based lyotropic nematic phases. We discuss in some detail how the transfer of orientational order from liquid crystal host to nanoparticle guest can be verified and which degree of ordering can be expected, as well as the importance of choosing the right surfactant and its concentration for the stability of the nanoparticle suspension. We introduce a method for dispersing nanoparticles with an absolute minimum of stabilizing surfactant, based on dispersion below the Krafft temperature, and we discuss the peculiar phenomenon of filament formation in lyotropic nematic phases with a sufficient concentration of well-dispersed carbon nanotubes. Finally, we describe how the total surfactant concentration in micellar nematics can be greatly reduced by combining cat- and anionic surfactants, and we discuss how nanotubes can help in inducing the liquid crystal phase close to the isotropic-nematic boundary.

  12. Morphological Analysis of White Cement Clinker Minerals: Discussion on the Crystallization-Related Defects

    Directory of Open Access Journals (Sweden)

    Mohamed Benmohamed

    2016-01-01

    Full Text Available The paper deals with a formation of artificial rock (clinker. Temperature plays the capital role in the manufacturing process. So, it is useful to analyze a poor clinker to identify the different phases and defects associated with their crystallization. X-ray fluorescence spectroscopy was used to determine the clinker’s chemical composition. The amounts of the mineralogical phases are measured by quantitative XRD analysis (Rietveld. Scanning electron microscopy (SEM was used to characterize the main phases of white Portland cement clinker and the defects associated with the formation of clinker mineral elements. The results of a study which focused on the identification of white clinker minerals and defects detected in these noncomplying clinkers such as fluctuation of the amount of the main phases (alite (C3S and belite (C2S, excess of the free lime, occurrence of C3S polymorphs, and occurrence of moderately-crystallized structures are presented in this paper.

  13. Shape effect related to crystallographic orientation of deformation behavior in copper crystals

    International Nuclear Information System (INIS)

    Kim, K.H.; Chang, C.H.; Koo, Y.M.; MacDowell, A.A.

    1999-01-01

    The deformation behavior of pure copper single crystals has been investigated by scanning electron microscopy and synchrotron radiation using the in situ reflection Laue method. Two types of samples with the same orientation of tensile axes, but with different crystallographic orientations in the directions of the width and thickness of the samples, have been studied. They showed different characteristics of deformation behavior, such as the activated slip systems, the movement of the tensile axis, and the mode of fracture

  14. Mirage, a food chain transfer and dosimetric impact code in relation with atmospheric and liquid dispersion codes

    International Nuclear Information System (INIS)

    Van Dorpe, F.; Jourdain, F.

    2006-01-01

    Full text: The numerical code M.I.R.A.G.E. (Module of Radiological impact calculations on the Environment due to accidental or chronic nuclear releases through Aqueous and Gas media) has been developed to simulate the radionuclides transfer in the biosphere and food chains, as well as the dosimetric impact on man, after accidental or chronic releases in the environment by nuclear installations. The originality of M.I.R.A.G.E. is to propose a single tool chained downstream with various atmospheric and liquid dispersion codes. The code M.I.R.A.G.E. is a series of modules which makes it possible to carry out evaluations on the transfers in food chains and human dose impact. Currently, M.I.R.A.G.E. is chained with a Gaussian atmospheric dispersion code H.A.R.M.A.T.T.A.N. (Cea), a 3 D atmospheric dispersion code with Lagrangian model named M.I.N.E.R.V.E.-S.P.R.A.Y. (Aria Technology) and a 3 D groundwater transfer code named M.A.R.T.H.E. (B.R.G.M.). M.I.R.A.G.E. uses concentration or activity result files as initial data input for its calculations. The application initially calculates the concentrations in the various compartments of the environment (soils, plants, animals). The results are given in the shape of concentration and dose maps and also on a particular place called a reference group for dosimetric impact (like a village or a specific population group located around a nuclear installation). The input and output data of M.I.R.A.G.E. can have geographic coordinates and thus readable by a G.I.S. M.I.R.A.G. E.is an opened system with which it is easy to chain other codes of dispersion that those currently used. The calculations uncoupled with dispersion calculations are also possible by manual seizure of the dispersion data (contamination of a tablecloth, particular value in a point, etc.). M.I.R.A.G.E. takes into account soil deposits and resuspension phenomenon, transfers in plants and animals (choice of agricultural parameters, types of plants and animals, etc

  15. Preparation and Single-Crystal X-Ray Structures of Four Related Mixed-Ligand 4-Methylpyridine Indium Halide Complexes

    Science.gov (United States)

    Hepp, Aloysius F.; Clark, Eric B.; Schupp, John D.; Williams, Jennifer N.; Duraj, Stan A.; Fanwick, Philip E.

    2013-01-01

    We describe the structures of four related indium complexes obtained during synthesis of solid-state materials precursors. Indium adducts of halides and 4-methylpyridine, InX3(pic)3 (X = Cl, Br; pic = 4-methylpyridine) consist of octahedral molecules with meridional (mer) geometry. Crystals of mer-InCl3(pic)3 (1) are triclinic, space group P1(bar) (No. 2), with a = 9.3240(3), b = 13.9580(6), c = 16.7268 (7) A, alpha = 84.323(2), beta = 80.938(2), gamma = 78.274(3)Z = 4, R = 0.035 for 8820 unique reflections. Crystals of mer-InBr3(pic)3 (2) are monoclinic, space group P21/n (No. 14), with a = 15.010(2), b = 19.938(2), c = 16.593(3), beta = 116.44(1)Z = 8, R = 0.053 for 4174 unique reflections. The synthesis and structures of related compounds with phenylsulfide (chloride) (3) and a dimeric complex with bridging hydroxide (bromide) (4) coordination is also described. Crystals of trans-In(SC6H5)Cl2(pic)3 (3) are monoclinic, space group P21/n (No. 14), with a = 9.5265(2), b = 17.8729(6), c = 13.8296(4), beta = 99.7640(15)Z = 4, R = 0.048 for 5511 unique reflections. Crystals of [In(mu-OH)Br2(pic)22 (4) are tetragonal, space group = I41cd (No. 110) with a = 19.8560(4), b = 19.8560(4), c = 25.9528(6), Z = 8, R = 0.039 for 5982 unique reflections.

  16. Consistency constraints on m{sub s} from QCD dispersion relations and chiral perturbation theory in K{sub l3} decays

    Energy Technology Data Exchange (ETDEWEB)

    Richard F. Lebed; Karl Schilcher

    1997-10-01

    The authors use both old and new theoretical developments in QCD dispersion relation constraints on the scalar form factor in the decay K {r_arrow} {pi}l{nu}{sub l} to obtain constraints on the strange quark mass. The perturbative QCD side of the calculation incorporates up to four-loop corrections, while the hadronic side uses a recently developed parameterization constructed explicitly to satisfy the dispersive constraints. Using chiral perturbation theory ({chi}PT) as a model for soon-to-be measured data, they find a series of lower bounds on m{sub s} increasing with the accuracy to which one believes {chi}PT to represent the full QCD result.

  17. Morphology of β-BaB2O4 (BBO) in relation to its crystal structure and growth conditions

    International Nuclear Information System (INIS)

    Bolt, R.J.; Bennema, P.

    1993-01-01

    A periodic-bond-chain (PBC) analysis has been made of the structure of β-BaB 2 O 4 (BBO) and related to crystal growth conditions, in order to explain the sometimes tangerine-shaped, sometimes needle-shaped crystals that are observed when BBO is grown experimentally. The periodic bond chains generate eight-connected nets in BBO. The order of morphological importance (MI) of these F faces is determined by comparing the nearest-neighbour interaction ionic bond energies. The results are compared with experimental data. Six faces, sometimes observed parallel to the c axis of BBO, were identified as the hexagonal prism {11 anti 20}. Two other forms are either the trigonal pyramids {01 anti 12} and {01 anti 1 anti 2} or the trigonal pyramids {10 anti 12} and {01 anti 1 anti 2}. {0001} is an important cleavage plane. The tangerine habit is a result of the strong temperature gradient, which is often used when growing BBO. The isotherms of the furnace impose their habit on the growing crystal. (orig.)

  18. Ferroelectric Nanoparticles in Liquid Crystals: Recent Progress and Current Challenges

    Science.gov (United States)

    Glushchenko, Anatoliy

    2017-01-01

    The dispersion of ferroelectric nanomaterials in liquid crystals has recently emerged as a promising way for the design of advanced and tunable electro-optical materials. The goal of this paper is a broad overview of the current technology, basic physical properties, and applications of ferroelectric nanoparticle/liquid crystal colloids. By compiling a great variety of experimental data and discussing it in the framework of existing theoretical models, both scientific and technological challenges of this rapidly developing field of liquid crystal nanoscience are identified. They can be broadly categorized into the following groups: (i) the control of the size, shape, and the ferroelectricity of nanoparticles; (ii) the production of a stable and aggregate-free dispersion of relatively small (~10 nm) ferroelectric nanoparticles in liquid crystals; (iii) the selection of liquid crystal materials the most suitable for the dispersion of nanoparticles; (iv) the choice of appropriate experimental procedures and control measurements to characterize liquid crystals doped with ferroelectric nanoparticles; and (v) the development and/or modification of theoretical and computational models to account for the complexity of the system under study. Possible ways to overcome the identified challenges along with future research directions are also discussed. PMID:29104276

  19. Ferroelectric Nanoparticles in Liquid Crystals: Recent Progress and Current Challenges.

    Science.gov (United States)

    Garbovskiy, Yuriy; Glushchenko, Anatoliy

    2017-11-01

    The dispersion of ferroelectric nanomaterials in liquid crystals has recently emerged as a promising way for the design of advanced and tunable electro-optical materials. The goal of this paper is a broad overview of the current technology, basic physical properties, and applications of ferroelectric nanoparticle/liquid crystal colloids. By compiling a great variety of experimental data and discussing it in the framework of existing theoretical models, both scientific and technological challenges of this rapidly developing field of liquid crystal nanoscience are identified. They can be broadly categorized into the following groups: (i) the control of the size, shape, and the ferroelectricity of nanoparticles; (ii) the production of a stable and aggregate-free dispersion of relatively small (~10 nm) ferroelectric nanoparticles in liquid crystals; (iii) the selection of liquid crystal materials the most suitable for the dispersion of nanoparticles; (iv) the choice of appropriate experimental procedures and control measurements to characterize liquid crystals doped with ferroelectric nanoparticles; and (v) the development and/or modification of theoretical and computational models to account for the complexity of the system under study. Possible ways to overcome the identified challenges along with future research directions are also discussed.

  20. The human ether-a-go-go-related gene (hERG) current inhibition selectively prolongs action potential of midmyocardial cells to augment transmural dispersion.

    Science.gov (United States)

    Yasuda, C; Yasuda, S; Yamashita, H; Okada, J; Hisada, T; Sugiura, S

    2015-08-01

    The majority of drug induced arrhythmias are related to the prolongation of action potential duration following inhibition of rapidly activating delayed rectifier potassium current (I(Kr)) mediated by the hERG channel. However, for arrhythmias to develop and be sustained, not only the prolongation of action potential duration but also its transmural dispersion are required. Herein, we evaluated the effect of hERG inhibition on transmural dispersion of action potential duration using the action potential clamp technique that combined an in silico myocyte model with the actual I(Kr) measurement. Whole cell I(Kr) current was measured in Chinese hamster ovary cells stably expressing the hERG channel. The measured current was coupled with models of ventricular endocardial, M-, and epicardial cells to calculate the action potentials. Action potentials were evaluated under control condition and in the presence of 1, 10, or 100 μM disopyramide, an hERG inhibitor. Disopyramide dose-dependently increased the action potential durations of the three cell types. However, action potential duration of M-cells increased disproportionately at higher doses, and was significantly different from that of epicardial and endocardial cells (dispersion of repolarization). By contrast, the effects of disopyramide on peak I(Kr) and instantaneous current-voltage relation were similar in all cell types. Simulation study suggested that the reduced repolarization reserve of M-cell with smaller amount of slowly activating delayed rectifier potassium current levels off at longer action potential duration to make such differences. The action potential clamp technique is useful for studying the mechanism of arrhythmogenesis by hERG inhibition through the transmural dispersion of repolarization.

  1. Low solubility in drug development: de-convoluting the relative importance of solvation and crystal packing.

    Science.gov (United States)

    Docherty, Robert; Pencheva, Klimentina; Abramov, Yuriy A

    2015-06-01

    An increasing trend towards low solubility is a major issue for drug development as formulation of low solubility compounds can be problematic. This paper presents a model which de-convolutes the solubility of pharmaceutical compounds into solvation and packing properties with the intention to understand the solubility limiting features. The Cambridge Crystallographic Database was the source of structural information. Lattice energies were calculated via force-field based approaches using Materials Studio. The solvation energies were calculated applying quantum chemistry models using Cosmotherm software. The solubilities of 54 drug-like compounds were mapped onto a solvation energy/crystal packing grid. Four quadrants were identified were different balances of solvation and packing were defining the solubility. A version of the model was developed which allows for the calculation of the two features even in absence of crystal structure. Although there are significant number of in-silico models, it has been proven very difficult to predict aqueous solubility accurately. Therefore, we have taken a different approach where the solubility is not predicted directly but is de-convoluted into two constituent features. © 2015 Royal Pharmaceutical Society.

  2. Ionic blocking effect in partially crystallized lithium disilicate

    International Nuclear Information System (INIS)

    Campos-Junior, Alvimar A.; Rodrigues, Ana C. M.

    2006-01-01

    A lithium disilicate glass was heat treated at 454 deg. C, the temperature of maximum nucleation rate, up to 25 days. At this temperature the growth rate is negligible, and therefore these thermal treatments lead to a glassy matrix in which ellipsoidal crystals of about the same size were randomly dispersed. Crystallized volume fraction (α) of up to 20% was reached. Electrical conductivity of glassy, partially crystallized, and 100% crystallized lithium disilicate was then measured by impedance spectroscopy. The crystallized surface layer was eliminated by polishing in order to solely analyze the effect of bulk crystals. The complex plane plots of impedance data showed one or two semicircles depending on (α). The high frequency semicircle represents the vitreous matrix while the low frequency one was ascribed to the blocking effect imposed to the lithium ions by the existing crystals in the partially crystallized samples. This hypothesis was confirmed by the analysis of the relaxation frequency related to each one of the semicircles and by comparison to the relaxation frequency of lithium disilicate glass and crystal. Results show that the blocking effect produces a second semicircle in the impedance diagram starting from a crystallized volume fraction of 15%

  3. Highly dispersed spherical Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} nanocrystals via topotactic crystallization of aggregation-free gel particles from an effective inverse miniemulsion sol–gel approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Aijun; Zeng, Yanwei, E-mail: zengyw-njut@126.com, E-mail: stephen-zeng@njtech.edu.cn, E-mail: stephen-zeng@163.com; Han, Longxiang; Ding, Chuan; Cao, Liangliang; Li, Rongjie [Nanjing Tech University, State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering (China)

    2015-09-15

    Aggregation-free spherical lanthanum-doped bismuth titanate (Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12}, BLT) gel particles with an average size of about 150 nm were successfully obtained from an inverse miniemulsion sol–gel process, with Span-80 acting as surfactant, n-butanol as co-surfactant, cyclohexane as continuous phase, and submicro-droplets of aqueous solution containing Bi{sup 3+}, La{sup 3+} and Ti{sup 4+} ions as dispersed phase, and then topotactically transformed into highly dispersed spherical BLT nanocrystals after an in situ crystallization at 600 °C for 8 h. It has been found that the BLT gel particles can be obtained via a moderate sol–gel reaction inside the miniemulsion droplets at 65 °C, but their morphology and aggregation degree are strongly affected by the relative amounts of Span-80 and n-butanol. The perfect spherical BLT gel particles with no aggregation can be achieved only under the condition of 3 wt% n-butanol relative to the mass of cyclohexane, with excessive amount of n-butanol leading to the formation of ill-gelled particles with irregular shapes, while insufficient addition of n-butanol resulting in terrible aggregation of gel particles. To understand the formation of aggregation-free spherical BLT gel particles, a tentative mechanism is proposed and discussed, which reveals that a well-coordinated oil–water interfacial film made up of Span-80 and n-butanol molecules and the appropriately enhanced evaporation of water from such interfaces should be responsible for the formation of aggregation-free spherical BLT gel particles. Graphical Abstract: Aggregation-free spherical BLT (Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12}) gel particles can be prepared from an effective inverse miniemulsion sol–gel process, and subsequently topotactically transformed into spherical BLT nanocrystals through an in situ crystallization.

  4. Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF)

    Science.gov (United States)

    Smith, Kevin T.; Balouet, Jean Christophe; Shortle, Walter C.; Chalot, Michel; Beaujard, François; Grudd, Håkan; Vroblesky, Don A.; Burkem, Joel G.

    2014-01-01

    Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to distinguish dendrochemical effects of internal processes from environmental contamination. Calcium, potassium, and zinc are three marker cations that illustrate the influence of these processes. We found changes in cation chemistry in tree rings potentially due to biomineralization, development of cracks or checks, heartwood/sapwood differentiation, intra-annual processes, and compartmentalization of infection. Distinguishing internal from external processes that affect dendrochemistry will enhance the value of EDXRF for both physiological and forensic investigations.

  5. Bosonic fields in crystal manifold

    Energy Technology Data Exchange (ETDEWEB)

    Alencar, G., E-mail: geovamaciel@gmail.com [Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici, 60440-554 Fortaleza, Ceará (Brazil); Tahim, M.O., E-mail: makarius.tahim@uece.br [Universidade Estadual do Ceará, Faculdade de Educação, Ciências e Letras do Sertão Central, Rua Epitácio Pessoa, 2554, 63.900-000 Quixadá, Ceará (Brazil); Landim, R.R., E-mail: renan@fisica.ufc.br [Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici, 60440-554 Fortaleza, Ceará (Brazil); Costa Filho, R.N., E-mail: rai@fisica.ufc.br [Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici, 60440-554 Fortaleza, Ceará (Brazil)

    2013-11-04

    A crystal-like universe made of membranes in extra dimensions in a Randall–Sundrum scenario is studied. A background gravitational metric satisfying the right boundary conditions is considered to study the localization of the scalar, gauge and Kalb–Ramond fields. It is found that the wave function for the fields are Bloch waves. The mass modes equations are calculated allowing us to show the zero-gap mass behavior and the mass dispersion relation for each field. Finally we generalize all these results and consider q-forms in the crystal membrane universe. We add the dilaton interaction in order to guarantee localization of forms. We show that, due to the dimension D, the form q and the dilaton coupling λ, the mass spectrum can be the same for the different bosonic fields studied. Such a result is a different way to see the duality between forms.

  6. All-in-One: Achieving Robust, Strongly Luminescent and Highly Dispersible Hybrid Materials by Combining Ionic and Coordinate Bonds in Molecular Crystals.

    Science.gov (United States)

    Liu, Wei; Zhu, Kun; Teat, Simon J; Dey, Gangotri; Shen, Zeqing; Wang, Lu; O'Carroll, Deirdre M; Li, Jing

    2017-07-12

    Extensive research has been pursued to develop low-cost and high-performance functional inorganic-organic hybrid materials for clean/renewable energy related applications. While great progress has been made in the recent years, some key challenges remain to be tackled. One major issue is the generally poor stability of these materials, which originates from relatively fragile/weak bonds between inorganic and organic constituents. Herein, we report a unique "all-in-one" (AIO) approach in constructing robust structures with desired properties. Such approach allows formation of both ionic and coordinate bonds within a molecular cluster, which greatly enhances structural stability while maintaining the molecular identity of the cluster and its high luminescence. The novel AIO structures are composed of various anionic (Cu m I m+n ) n- clusters and cationic N-ligands. They exhibit high luminescence efficiency, significantly improved chemical, thermal and moisture stability, and excellent solution processability. Both temperature dependent photoluminescence experiments and DFT calculations are performed to investigate the luminescence origin and emission mechanism of these materials, and their suitability as energy-saving LED lighting phosphors is assessed. This study offers a new material designing strategy that may be generalized to many other material classes.

  7. Irradiation-related amorphization and crystallization: In situ transmission electron microscope studies

    International Nuclear Information System (INIS)

    Allen, C.W.

    1994-01-01

    Interfacing an ion accelerator to a transmission electron microscope (TEM) allows the analytical functions of TEM imaging and diffraction to be employed during ion-irradiation effects studies. At present there are twelve such installations in Japan, one in France and one in the US. This paper treats several aspects of in situ studies involving electron and ion beam induced and enhanced phase transformations and presents results of several in situ experiments to illustrate the dynamics of this approach in the materials science of irradiation effects. The paper describes the ion- and electron-induced amorphization of CuTi; the ion-irradiation-enhanced transformation of TiCr 2 ; and the ion- and electron-irradiation-enhanced crystallization of CoSi 2

  8. InP/ZnS quantum-dot-dispersed nematic liquid crystal illustrating characteristic birefringence and enhanced electro-optical parameters

    Science.gov (United States)

    Roy, Aradhana; Pathak, Govind; Herman, Jakub; Inamdar, Sanjeev R.; Srivastava, Atul; Manohar, Rajiv

    2018-03-01

    The present study investigates the influence of InP/ZnS core/shell QDs on various parameters of Nematic LC sample 1832A, based on 4-(4-alkyl-cyclohexyl)benzene isothiocyanates and 4-(4-alkyl-cyclohexyl)biphenyl isothiocyanates. Observations recorded consist of distinguished functioning of birefringence phenomenon along with characteristic response time measurement. Further study of rotational viscosity and splay elastic constant portrays stupendous behavior strengthening the appositeness of the composites for low-charge consumable devices. The addition of 0.2 ml of core/shell QDs producing more than two times faster response and enhanced birefringence at low-temperature range can be employed in development of thermostable photonic devices. In addition, dielectric properties comprising of relative permittivity and conductivity have been reported supporting the outcome of the investigation in applicative LC-based technologies.

  9. Polypyrrole: FeOx·ZnO nanoparticle solar cells with breakthrough open-circuit voltage prepared from relatively stable liquid dispersions

    KAUST Repository

    Zong, Baoyu

    2014-01-01

    Organic hybrid solar cells with a large open-circuit voltage, up to above that of 1.5 V standard battery voltage, were demonstrated using blends of polypyrrole: Fe2O3·ZnO nanoparticles as active-layers. The cell active-layers were readily coated in open air from relatively stable liquid dark-color polypyrrole-based dispersions, which were synthesized using appropriate surfactants during the in situ polymerization of pyrrole with FeCl3 or both H2O2 and FeCl3 as the oxidizers. The performance of the cells depends largely on the synthesized blend phase, which is determined by the surfactants, oxidizers, as well as the reactant ratio. Only the solar cells fabricated from the stable dispersions can produce both a high open-circuit voltage (>1.0 V) and short-circuit current (up to 7.5 mA cm-2) due to the relatively uniform porous network nanomorphology and higher shunt to series resistance ratio of the active-layers. The cells also display a relatively high power-conversion efficiency of up to ∼3.8%. This journal is

  10. Fickian dispersion is anomalous

    Science.gov (United States)

    Cushman, John H.; O'Malley, Dan

    2015-12-01

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  11. Magnesium sulfate salts and historic building materials: experimental simulation of limestone flaking by relative humidity cycling and crystallization of salts

    Directory of Open Access Journals (Sweden)

    Pinchin, S.

    2008-06-01

    Full Text Available Magnesium sulfate salts often result from the combination of incompatible construction materials, such as stone or mortar with high magnesium content and sulfates from adjacent mortars or polluted air. When combined with a source of moisture, these materials react to form soluble salts, often leading to significant damage by flaking of the stone, as the magnesium sulfate responds to fluctuating environmental conditions. Several laboratory experiments were performed to reproduce surface flaking on different types of limestone from Spain and the UK to evaluate the effects of humidity cycling on the damage of stone by salt crystallization. The two salt solutions used for the experiments were a single salt of magnesium sulfate and a mixture of magnesium sulfate, calcium sulfate and sodium chloride, a typical salt mixture found in damaged stone at the site of Howden Minster (UK. A climate chamber with precise and programmable temperature and humidity control was used to test the hypothesis that salt damage in the stone can be readily caused by humidity fluctuations. Damage was monitored using Linear Variable Differential Transformer (LVDT, which measure transducers displacement by dimensional change on the order of microns. In addition, Ion Chromatography, Environmental Scanning Electron Microscopy with energy dispersive X-ray spectroscopy (ESEM-EDX and X-ray Diffraction analyses (XRD were also carried out to analyze salt behavior. Damage by flaking took place in two types of magnesian limestone cubes impregnated with the salt mixture, from Cadeby quarry and York Minster, apparently by deliquescent salts of low equilibrium relative humidity (RHeq, while the rest of the samples developed a salt crust over the surface, but no damage was observed in the stone. It is important to verify hypotheses developed from field observations with laboratory experiments. By combining both field and laboratory data, a clearer understanding the different mechanisms of

  12. Nanomechanical investigation of ion implanted single crystals - Challenges, possibilities and pitfall traps related to nanoindentation

    Science.gov (United States)

    Kurpaska, Lukasz

    2017-10-01

    Nanoindentation technique have developed considerably over last thirty years. Nowadays, commercially available systems offer very precise measurement in nano- and microscale, environmental noise cancelling (or at least noise suppressing), in situ high temperature indentation in controlled atmosphere and vacuum conditions and different additional options, among them dedicated indentation is one of the most popular. Due to its high precision, and ability to measure mechanical properties from very small depths (tens of nm), this technique become quite popular in the nuclear society. It is known that ion implantation (to some extent) can simulate the influence of neutron flux. However, depth of the material damage is very limited resulting in creation of thin layer of modified material over unmodified bulk. Therefore, only very precise technique, offering possibility to control depth of the measurement can be used to study functional properties of the material. For this reason, nanoindentation technique seems to be a perfect tool to investigate mechanical properties of ion implanted specimens. However, conducting correct nanomechanical experiment and extracting valuable mechanical parameters is not an easy task. In this paper a discussion about the nanoindentation tests performed on ion irradiated YSZ single crystal is presented. The goal of this paper is to discuss possible traps when studying mechanical properties of such materials and thin coatings.

  13. Relation between the swelling and the disordering in ionic crystals irradiated by fast heavy ions

    International Nuclear Information System (INIS)

    Boccanfuso, M.

    2001-12-01

    When fast heavy ions penetrate in matter, they slow down essentially by depositing their energy on the electrons. This can lead to strong electronic excitation densities in the solid and then to structural modifications. In this work, calcium fluoride (CaF 2 ) was used to look further into the damage induced by irradiation with fast heavy ions in ionic crystals. Four techniques were mainly employed to characterise this damage. These techniques of analysis are wide angle X-ray diffraction, surface profilometry, Rutherford backscattering spectrometry and UV-visible optical absorption spectroscopy. The results of this work show that CaF 2 answers in a multiple way to the electronic excitations. For stopping powers higher than approximately 5 keV/nm, a polygonization seems to occur. This causes a structural disorder, a swelling of 0.27 % and the formation of fractures in the material. A second damage mechanism is caused above approximately 13 keV/nm and results in a loss of the initial crystalline structure. However, optical centres appear whatever the ion stopping power, which indicates that these defects cannot be the cause of the two above mentioned damage mechanisms. According to a thermal spike model, the two thresholds can be linked to melting and sublimation energy of the material, respectively. (author)

  14. Phase relations study on the melting and crystallization regions of the Bi-2223 high temperature superconductor

    Directory of Open Access Journals (Sweden)

    Polasek Alexander

    2004-01-01

    Full Text Available The melting and solidification behavior of Bi2Sr2Ca2Cu3 O10 (Bi-2223 precursors has been studied. Nominal compositions corresponding to excess of liquid, Ca2CuO3 and CuO have been investigated. Each sample was made by packing a precursor powder into a silver crucible, in order to approximately simulate the situation found in 2223 silver-sheathed tapes. The samples were partially melted and then slow-cooled, being quenched from different temperatures and analyzed through X-ray diffraction (XRD and scanning electron microscopy (SEM/EDS. The precursors decomposed peritectically during melting, forming liquid and solid phases. Very long plates with compositions falling in the vicinity of the 2223 primary phase field formed upon slow-cooling. The 2223 phase may have been formed and the results suggest that long grains of this phase might be obtained by melting and crystallization if the exact peritectic region and the optimum processing conditions are found.

  15. Dispersion bias, dispersion effect, and the aerosol-cloud conundrum

    International Nuclear Information System (INIS)

    Liu Yangang; Daum, Peter H; Guo Huan; Peng Yiran

    2008-01-01

    This work examines the influences of relative dispersion (the ratio of the standard deviation to the mean radius of the cloud droplet size distribution) on cloud albedo and cloud radiative forcing, derives an analytical formulation that accounts explicitly for the contribution from droplet concentration and relative dispersion, and presents a new approach to parameterize relative dispersion in climate models. It is shown that inadequate representation of relative dispersion in climate models leads to an overestimation of cloud albedo, resulting in a negative bias of global mean shortwave cloud radiative forcing that can be comparable to the warming caused by doubling CO 2 in magnitude, and that this dispersion bias is likely near its maximum for ambient clouds. Relative dispersion is empirically expressed as a function of the quotient between cloud liquid water content and droplet concentration (i.e., water per droplet), yielding an analytical formulation for the first aerosol indirect effect. Further analysis of the new expression reveals that the dispersion effect not only offsets the cooling from the Twomey effect, but is also proportional to the Twomey effect in magnitude. These results suggest that unrealistic representation of relative dispersion in cloud parameterization in general, and evaluation of aerosol indirect effects in particular, is at least in part responsible for several outstanding puzzles of the aerosol-cloud conundrum: for example, overestimation of cloud radiative cooling by climate models compared to satellite observations; large uncertainty and discrepancy in estimates of the aerosol indirect effect; and the lack of interhemispheric difference in cloud albedo.

  16. Quantum dimer model on the triangular lattice: Semiclassical and variational approaches to vison dispersion and condensation

    Science.gov (United States)

    Misguich, Grégoire; Mila, Frédéric

    2008-04-01

    After reviewing the concept of vison excitations in Z2 dimer liquids, we study the liquid-crystal transition of the quantum dimer model on the triangular lattice by means of a semiclassical spin-wave approximation to the dispersion of visons in the context of a “soft-dimer” version of the model. This approach captures some important qualitative features of the transition: continuous nature of the transition, linear dispersion at the critical point, and 12×12 symmetry-breaking pattern. In a second part, we present a variational calculation of the vison dispersion relation at the Rokhsar-Kivelson (RK) point, which reproduces the qualitative shape of the dispersion relation and the order of magnitude of the gap. This approach provides a simple but reliable approximation of the vison wave functions at the RK point.

  17. Can dispersal investment explain why tall plant species achieve longer dispersal distances than short plant species?

    Science.gov (United States)

    Thomson, Fiona J; Letten, Andrew D; Tamme, Riin; Edwards, Will; Moles, Angela T

    2018-01-01

    Tall plant species disperse further distances than do short species, within and across dispersal syndromes, yet the driver underpinning this relationship is unclear. The ability of taller plants to invest more in dispersal structures may explain the positive relationship between plant height and dispersal distance. Here, we quantify the cross-species relationships between presence of dispersal structures, dispersal investment plant height and dispersal distance. Plant height, dispersal syndrome and dispersal investment data were collated for 1613 species from the literature, with dispersal distance data collated for 114 species. We find that species with high dispersal investment disperse further than do species with low dispersal investment. Tall species have a greater probability of having dispersal structures on their seeds compared with short species. For species with dispersal structures on their seeds, plant height is very weakly related to dispersal investment. Our results provide the first global confirmation of the dispersal investment-distance hypothesis, and show dispersal investment can be used for predicting species dispersal distances. However, our results and those of previous studies indicate plant height is still the best proxy for estimating species dispersal distances due to it being such a readily available plant trait. © 2017 Landcare Research. New Phytologist © 2017 New Phytologist Trust.

  18. Neutron-Phonon Interaction Studies in Copper, Zinc and Magnesium Single Crystals

    International Nuclear Information System (INIS)

    Maliszewski, E.; Sosnowski, J.; Blinowski, K.; Kozubowski, J.; Padlo, L.; Sledziewska, D.

    1963-01-01

    The phonon dispersion relations in copper single crystals has been studied by means of a triple-axis crystal neutron spectrometer. In the [100] direction the transversal branch, not reported in the papers of Cabie and Jacrot, has been found. This branch fits well to the recent data of sound velocity; however, it differs partly from the X-ray results of Jacobsen. For the longitudinal branch in the [100] direction the dispersion curve obtained by Cribier and Jacrot is lying well above the Jacobsen's curve, and the experimental points reported in the present paper support the results of Cribier and Jacrot. The phonon dispersion relations in zinc and magnesium single crystals has been studied using the cold neutron method and by means of a triple-axis crystal neutron spectrometer as well. The scattering surfaces in the [1010] plane were traced, the AT and AL branches found and the phonon dispersion relations in the [001] and [010] directions obtained. The results have been compared with those obtained by Johnson with X-rays. In the [001] direction the present results fit well lo Johnson's foe the AL branch. In the [010] direction for the AT branch a large discrepancy has been found between Johnson's and the present results. Some explanation of this discrepancy is given. Similar measurements in the same directions in magnesium single crystals are under way and will be reported. (author) [fr

  19. Dispersal phenology of hydrochorous plants in relation to discharge, seed release time and buoyancy of seeds: the flood pulse concept supported

    NARCIS (Netherlands)

    Boedeltje, G.; Bakker, J.P.; Brinke, A. Ten; Groenendael, J.M. van; Soesbergen, M.

    2004-01-01

    1 Restored floodplains and backwaters lacking a viable propagule bank, may need flood pulses to facilitate inward dispersal of diaspores. Temporal patterns of hydrochorous plant dispersal are, however, not well known. 2 Diversity and abundance of diaspores dispersed in a water body over 12 months

  20. Dispersal phenology of hydrochorous plants in relation to discharge, seed release time and buoyancy of seeds : the flood pulse concept supported

    NARCIS (Netherlands)

    Boedeltje, G; Bakker, JP; Ten Brinke, A; Van Groenendael, JM; Soesbergen, M

    2004-01-01

    1 Restored floodplains and backwaters lacking a viable propagule bank, may need flood pulses to facilitate inward dispersal of diaspores. Temporal patterns of hydrochorous plant dispersal are, however, not well known. 2 Diversity and abundance of diaspores dispersed in a water body over 12 months

  1. The Higgs boson and the quark top in the formalism of dispersion relations and the standard model

    International Nuclear Information System (INIS)

    Bouayed, N.

    2008-11-01

    the electroweak interaction enters a strong interaction regime where perturbative unitarity may be violated, so we have to resort to non-perturbative methods. By following the pioneering work of Contogouris, I construct a dispersive model for the process W L W L → W L W L where W L is the longitudinal W. The numerical resolution of the integral equation that is induced by this model enables a study of the strong effects of the electroweak interaction at high energies. I also extract a new limit for the validity of the perturbative calculation in the electroweak theory and a value for the Higgs mass in case the Higgs is very heavy. (author)

  2. On estimates of the pion-nucleon sigma term by the dispersion relations and taking into account the interrelation between the chiral and scale invariance breaking

    International Nuclear Information System (INIS)

    Efrosinin, V.P.; Zaikin, D.A.

    1983-01-01

    Possible reasons of disagreement between estimates of the pion-nucleon σ term obtained by the method of dispersion relations with extrapolation to the Chang-Dashen point and by alternative methods, making no use of such extrapolation are investigated. One of the reasons may be, that the πN amplitude is not analytic in the variable t at ν=0. A method, which is not so strongly influenced by the nonanalyticity, is suggested to estimate the σ term making use of the threshold data for the πN amplitude. Relation between the scale and chiral invariance breakings is discussed and the resulting estimate of the σ term is presented. Both estimates give close results (42 and 34 MeV) which do not contradict one another within the uncertainties of the methods

  3. Active Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Ek, Sara

    This thesis deals with the fabrication and characterization of active photonic crystal waveguides, realized in III-V semiconductor material with embedded active layers. The platform offering active photonic crystal waveguides has many potential applications. One of these is a compact photonic...... crystal semiconductor optical amplier. As a step towards such a component, photonic crystal waveguides with a single quantum well, 10 quantum wells and three layers of quantum dots are fabricated and characterized. An experimental study of the amplied spontaneous emission and a implied transmission...... are presented in this thesis. A variation of photonic crystal design parameters are used leading to a spectral shift of the dispersion, it is veried that the observed effects shift accordingly. An enhancement of the amplified spontaneous emission was observed close to the band edge, where light is slowed down...

  4. A simple model for the surface energy of ionic crystals

    International Nuclear Information System (INIS)

    Roman, E.; Tosi, M.P.

    1982-01-01

    The surface energy of ionic materials is empirically related to bulk properties (elastic constants, electronic dielectric constant and optical band gap) through an analysis of the cleavage force. This is evaluated at small and large separations of the two crystal halves from phonon dispersion curves and from van der Waals interactions, respectively, and these two limiting behaviours are connected by a scaling hypothesis introduced for metals by Kohn and Yaniv. The experimental data that are available for a few ionic crystals seem to satisfy the suggested relation, with an empirical universal parameter which has roughly the same value as determined for metals. (author)

  5. Interface, a dispersed architecture

    NARCIS (Netherlands)

    Vissers, C.A.

    1976-01-01

    Past and current specification techniques use timing diagrams and written text to describe the phenomenology of an interface. This paper treats an interface as the architecture of a number of processes, which are dispersed over the related system parts and the message path. This approach yields a

  6. Relating river discharge and water temperature to the recruitment of age‐0 White Sturgeon (Acipenser transmontanus Richardson, 1836) in the Columbia River using over‐dispersed catch data

    Science.gov (United States)

    Counihan, Timothy D.; Chapman, Colin G.

    2018-01-01

    The goals were to (i) determine if river discharge and water temperature during various early life history stages were predictors of age‐0 White Sturgeon, Acipenser transmontanus, recruitment, and (ii) provide an example of how over‐dispersed catch data, including data with many zero observations, can be used to better understand the effects of regulated rivers on the productivity of depressed sturgeon populations. An information theoretic approach was used to develop and select negative binomial and zero‐inflated negative binomial models that model the relation of age‐0 White Sturgeon survey data from three contiguous Columbia River reservoirs to river discharge and water temperature during spawning, egg incubation, larval, and post‐larval phases. Age‐0 White Sturgeon were collected with small mesh gill nets in The Dalles and John Day reservoirs from 1997 to 2014 and a bottom trawl in Bonneville Reservoir from 1989 to 2006. Results suggest that seasonal river discharge was positively correlated with age‐0 recruitment; notably that discharge, 16 June–31 July was positively correlated to age‐0 recruitment in all three reservoirs. The best approximating models for two of the three reservoirs also suggest that seasonal water temperature may be a determinant of age‐0 recruitment. Our research demonstrates how over‐dispersed catch data can be used to better understand the effects of environmental conditions on sturgeon populations caused by the construction and operation of dams.

  7. Diurnal Patterns in dispersal of Monilinia fructigena conidia in an apple orchard in relation to weather factors

    NARCIS (Netherlands)

    Bannon, F.; Gort, G.; Leeuwen, van G.; Holb, I.; Jeger, M.J.

    2009-01-01

    The aerial concentration of Monilinia fructigena (causing brown rot in pome fruit) conidia was sampled during 1997 and 1998 in an apple orchard and was related to weather conditions. The highest hourly concentration measured in 1997 was 230 conidia/m3, in 1998 concentrations were lower than in 1997

  8. Semi-Dirac points in phononic crystals

    KAUST Repository

    Zhang, Xiujuan

    2014-01-01

    A semi-Dirac cone refers to a peculiar type of dispersion relation that is linear along the symmetry line but quadratic in the perpendicular direction. It was originally discovered in electron systems, in which the associated quasi-particles are massless along one direction, like those in graphene, but effective-mass-like along the other. It was reported that a semi-Dirac point is associated with the topological phase transition between a semi-metallic phase and a band insulator. Very recently, the classical analogy of a semi-Dirac cone has been reported in an electromagnetic system. Here, we demonstrate that, by accidental degeneracy, two-dimensional phononic crystals consisting of square arrays of elliptical cylinders embedded in water are also able to produce the particular dispersion relation of a semi-Dirac cone in the center of the Brillouin zone. A perturbation method is used to evaluate the linear slope and to affirm that the dispersion relation is a semi-Dirac type. If the scatterers are made of rubber, in which the acoustic wave velocity is lower than that in water, the semi-Dirac dispersion can be characterized by an effective medium theory. The effective medium parameters link the semi-Dirac point to a topological transition in the iso-frequency surface of the phononic crystal, in which an open hyperbola is changed into a closed ellipse. This topological transition results in drastic change in wave manipulation. On the other hand, the theory also reveals that the phononic crystal is a double-zero-index material along the x-direction and photonic-band-edge material along the perpendicular direction (y-direction). If the scatterers are made of steel, in which the acoustic wave velocity is higher than that in water, the effective medium description fails, even though the semi-Dirac dispersion relation looks similar to that in the previous case. Therefore different wave transport behavior is expected. The semi-Dirac points in phononic crystals described in

  9. Phonon dispersion in vanadium

    International Nuclear Information System (INIS)

    Ivanov, A.S.; Rumiantsev, A.Yu.

    1999-01-01

    Complete text of publication follows. Phonon dispersion curves in Vanadium metal are investigated by neutron inelastic scattering using three-axis spectrometers. Due to extremely low coherent scattering amplitude of neutrons in natural isotope mixture of vanadium the phonon frequencies could be determined in the energy range below about 15 meV. Several phonon groups were measured with the polarised neutron scattering set-up. It is demonstrated that the intensity of coherent inelastic scattering observed in the non-spin-flip channel vanishes in the spin-flip channel. The phonon density of states is measured on a single crystal keeping the momentum transfer equal to a vector of reciprocal lattice where the coherent inelastic scattering is suppressed. Phonon dispersion curves in vanadium, as measured by neutron and earlier by X-ray scattering, are described in frames of a charge-fluctuation model involving monopolar and dipolar degrees of freedom. The model parameters are compared for different transition metals with body-centred cubic-structure. (author)

  10. Multiple Linear Regression Modeling To Predict the Stability of Polymer-Drug Solid Dispersions: Comparison of the Effects of Polymers and Manufacturing Methods on Solid Dispersion Stability.

    Science.gov (United States)

    Fridgeirsdottir, Gudrun A; Harris, Robert J; Dryden, Ian L; Fischer, Peter M; Roberts, Clive J

    2018-03-29

    Solid dispersions can be a successful way to enhance the bioavailability of poorly soluble drugs. Here 60 solid dispersion formulations were produced using ten chemically diverse, neutral, poorly soluble drugs, three commonly used polymers, and two manufacturing techniques, spray-drying and melt extrusion. Each formulation underwent a six-month stability study at accelerated conditions, 40 °C and 75% relative humidity (RH). Significant differences in times to crystallization (onset of crystallization) were observed between both the different polymers and the two processing methods. Stability from zero days to over one year was observed. The extensive experimental data set obtained from this stability study was used to build multiple linear regression models to correlate physicochemical properties of the active pharmaceutical ingredients (API) with the stability data. The purpose of these models is to indicate which combination of processing method and polymer carrier is most likely to give a stable solid dispersion. Six quantitative mathematical multiple linear regression-based models were produced based on selection of the most influential independent physical and chemical parameters from a set of 33 possible factors, one model for each combination of polymer and processing method, with good predictability of stability. Three general rules are proposed from these models for the formulation development of suitably stable solid dispersions. Namely, increased stability is correlated with increased glass transition temperature ( T g ) of solid dispersions, as well as decreased number of H-bond donors and increased molecular flexibility (such as rotatable bonds and ring count) of the drug molecule.

  11. Crystal electric field-phonon interaction in NdCu2

    International Nuclear Information System (INIS)

    Hense, K.; Gratz, E.; Nowotny, H.; Loewenhaupt, M.; Hoser, A.

    2004-01-01

    A comparison of the crystal electric field (CF)-level schema of NdCu 2 and its measured phonon dispersion relation suggests that some of the phonon branches should show a measurable coupling with the CF. The presented inelastic neutron scattering data obtained from triple axis spectrometer measurements confirm this interaction. In addition, a theoretical model describing the experimental data is presented

  12. Transfer Matrix for Obliquely Incident Electromagnetic Waves Propagating in One Dimension Plasma Photonic Crystals

    International Nuclear Information System (INIS)

    Guo Bin

    2009-01-01

    Based on the electromagnetic theory and by using an analytical technique-the transfer matrix method, the obliquely incident electromagnetic waves propagating in one-dimension plasma photonic crystals is studied. The dispersion relations for both the P-polarization waves and S-polarization waves, depending on the plasma density, plasma thickness and period, are discussed. (basic plasma phenomena)

  13. Tunneling recombination luminescence under excitation of PbWO4:Mo crystals in the defect-related absorption region

    International Nuclear Information System (INIS)

    Fabeni, P.; Krasnikov, A.; Kaerner, T.; Laguta, V.V.; Nikl, M.; Pazzi, G.P.; Zazubovich, S.

    2009-01-01

    Time-resolved emission and excitation spectra and luminescence decay kinetics were studied at 150-300 K for the green emission of PbWO 4 :Mo crystals. It was found that the slow (μs-ms) decay component observed under excitation in the defect-related absorption region (around 3.8-3.9 eV) arises from the G(II) emission which appears at the tunneling recombination of optically created electron and hole centers. The study of the emission decay kinetics at different temperatures and excitation intensities allowed concluding that both the monomolecular and the bimolecular tunneling recombination process can be stimulated in the mentioned energy range. The monomolecular process takes place in the isolated spatially correlated pairs of electron and hole centers produced without release of electrons into the conduction band. The bimolecular process takes place in the pairs of randomly distributed centers created at the trapping of free electrons from the conduction band. The formation of electron centers under irradiation in the defect-related absorption region was investigated by the electron spin resonance (ESR) and thermally stimulated luminescence (TSL) methods. The possibility of various photo-thermally stimulated defects creation processes, which take place with and without release of free electrons into the conduction band, was confirmed.

  14. Radiation damage studies on NaBi(WO4)2 single crystals through oxygen related defects

    International Nuclear Information System (INIS)

    Singh, S.G.; Tyagi, M.; Desai, D.G.; Singh, A.K.; Gadkari, S.C.

    2010-01-01

    Single crystals of NaBi(WO 4 ) 2 grown under different conditions were studied for their radiation hardness to high gamma radiation doses (10 5 and 10 6 Gy) employing high dose rates (∼2 Gy/s). Annealing studies in oxygen as well as in vacuum were carried out and a relation between oxygen defects and irradiation induced damages has been proposed. Induced absorption spectra of irradiated and annealed samples were calculated and 5 individual peaks around 3.1, 2.8, 2.6, 2 and 1.7 eV related to different defect centers have been identified. Recovery of the transmission characteristics after the heavy irradiation was monitored at room temperatures (20±2 o C) and the corresponding lifetime has been found to be about 50 days. The thermoluminescence glow curve has been recorded and the activation energy of the defect centers was calculated as 0.9 eV using an initial rising method.

  15. High-pressure crystallization vs. recrystallization origin of garnet pyroxenite-eclogite within subduction related lithologies

    Science.gov (United States)

    Faryad, S. W.; Jedlicka, R.; Hauzenberger, C.; Racek, M.

    2018-03-01

    Mafic layers displaying transition between clinopyroxenite and eclogite within peridotite from felsic granulite in the Bohemian Massif (Lower Austria) have been investigated. The mafic-ultramafic bodies shared a common granulite facies metamorphism with its hosting felsic rocks, but they still preserve evidence of eclogite facies metamorphism. The selected mafic layer for this study is represented by garnet with omphacite in the core of coarse-grained clinopyroxene, while fine-grained clinopyroxene in the matrix is diopside. In addition, garnet contains inclusions of omphacite, alkali feldspars, hydrous and other phases with halogens and/or CO2. Textural relations along with compositional zoning in garnet from the clinopyroxenite-eclogite layers favour solid-state recrystallization of the precursor minerals in the inclusions and formation of garnet and omphacite during subduction. Textures and major and trace element distribution in garnet indicate two stages of garnet growth that record eclogite facies and subsequent granulite facies overprint. The possible model explaining the textural and compositional changes of minerals is that the granulite facies overprint occurred after formation and exhumation of the eclogite facies rocks.

  16. Better resolved low frequency dispersions by the apt use of Kramers-Kronig relations, differential operators and all-in-1 modelling

    Directory of Open Access Journals (Sweden)

    Jan van Turnhout

    2016-05-01

    Full Text Available The dielectric spectra of colloidal systems often contain a typical low frequency dispersion, which usually remains unnoticed, because of the presence of strong conduction losses. The KK relations offer a means for converting  into  data. This allows us to calculate conduction free  spectra in which the l.f. dispersion will show up undisturbed. This interconversion can be done on line with a moving frame of logarithmically spaced  data. The coefficients of the conversion frames were obtained by kernel matching and by using symbolic differential operators. Logarithmic derivatives and differences of  and  provide another option for conduction free data analysis. These difference-based functions actually derived from approximations to the distribution function, have the additional advantage of improving the resolution power of dielectric studies. A high resolution is important because of the rich relaxation structure of colloidal suspensions. The development of all-in-1 modelling facilitates the conduction free and high resolution data analysis. This mathematical tool allows the apart-together fitting of multiple data and multiple model functions. It proved also useful to go around the KK conversion altogether. This was achieved by the combined approximating  and  data with a complex rational fractional power function. The all-in-1 minimization turned out to be also highly useful for the dielectric modelling of a suspension with the complex dipolar coefficient. It guarantees a secure correction for the electrode polarization, so that the modelling with the help of the differences  and  can zoom in on the genuine colloidal relaxations.

  17. Binary photonic crystal for refractometric applications (TE case)

    Science.gov (United States)

    Taya, Sofyan A.; Shaheen, Somaia A.

    2017-11-01

    In this work, a binary photonic crystal is proposed as a refractometric sensor. The dispersion relation and the sensitivity are derived for transverse electric (TE) mode. In our analysis, the first layer is considered to be the analyte layer and the second layer is assumed to be left-handed material (LHM), dielectric or metal. It is found that the sensitivity of the LHM structure is the highest among other structures. It is possible for LHM photonic crystal to achieve a sensitivity improvement of 412% compared to conventional slab waveguide sensor.

  18. Band structures and localization properties of aperiodic layered phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yan Zhizhong, E-mail: zzyan@bit.edu.cn [Department of Applied Mathematics, Beijing Institute of Technology, Beijing 100081 (China); Zhang Chuanzeng [Department of Civil Engineering, University of Siegen, D-57078 Siegen (Germany)

    2012-03-15

    The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.

  19. Acousto-optical phonon excitation in cubic piezoelectric slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Willatzen, Morten; Duggen, Lars

    2017-01-01

    In this paper we investigate theoretically the influence of piezoelectric coupling on phonon dispersion relations. Specifically we solve dispersion relations for a fully coupled zinc-blende freestanding quantum well for different orientations of the crystal unit cell. It is shown that the phonon...... mode density in GaAs can change by a factor of approximately 2–3 at qx a = 1 for different crystal-growth directions relative to the slab thickness direction. In particular, it is found that optical and acoustic phonon modes are always piezoelectrically coupled, independent of the crystal...... that the piezoelectric effect leads to a drastically enhanced coupling of acoustic and optical phonon modes and increase in the local phonon density of states near the plasma frequency where the permittivity approaches zero....

  20. Variation in local abundance and species richness of stream fishes in relation to dispersal barriers: Implications for management and conservation

    Science.gov (United States)

    Nislow, K.H.; Hudy, M.; Letcher, B.H.; Smith, E.P.

    2011-01-01

    1.Barriers to immigration, all else being equal, should in principle depress local abundance and reduce local species richness. These issues are particularly relevant to stream-dwelling species when improperly designed road crossings act as barriers to migration with potential impacts on the viability of upstream populations. However, because abundance and richness are highly spatially and temporally heterogeneous and the relative importance of immigration on demography is uncertain, population- and community-level effects can be difficult to detect. 2.In this study, we tested the effects of potential barriers to upstream movements on the local abundance and species richness of a diverse assemblage of resident stream fishes in the Monongahela National Forest, West Virginia, U.S.A. Fishes were sampled using simple standard techniques above- and below road crossings that were either likely or unlikely to be barriers to upstream fish movements (based on physical dimensions of the crossing). We predicted that abundance of resident fishes would be lower in the upstream sections of streams with predicted impassable barriers, that the strength of the effect would vary among species and that variable effects on abundance would translate into lower species richness. 3.Supporting these predictions, the statistical model that best accounted for variation in abundance and species richness included a significant interaction between location (upstream or downstream of crossing) and type (passable or impassable crossing). Stream sections located above predicated impassable culverts had fewer than half the number of species and less than half the total fish abundance, while stream sections above and below passable culverts had essentially equivalent richness and abundance. 4.Our results are consistent with the importance of immigration and population connectivity to local abundance and species richness of stream fishes. In turn, these results suggest that when measured at

  1. Nonlinear Photonic Crystal Fibers

    DEFF Research Database (Denmark)

    Hansen, Kim Per

    2004-01-01

    Despite the general recession in the global economy and the collapse of the optical telecommunication market, research within specialty fibers is thriving. This is, more than anything else, due to the technology transition from standard all-glass fibers to photonic crystal fibers, which, instead...... of doping, use a microstructure of air and glass to obtain a refractive index difference between the core and the cladding. This air/glass microstructure lends the photonic crystal fibers a range of unique and highly usable properties, which are very different from those found in solid standard fibers......, leading to reduced mode confinement and dispersion flexibility. In this thesis, we treat the nonlinear photonic crystal fiber – a special sub-class of photonic crystal fibers, the core of which has a diameter comparable to the wavelength of the light guided in the fiber. The small core results in a large...

  2. Preparation of TiC single crystals

    International Nuclear Information System (INIS)

    Scheerer, B.; Fink, J.; Reichardt, W.

    1975-07-01

    TiC single crystals were prepared by vertical zone melting for measurements of the phonon dispersion by inelastic neutron scattering. The influence of the starting material and of the growing conditions on the growth of the crystal were studied. The crystals were characterized by chemical methods, EMX and neutron diffraction. It was possible to grow single crystals with a volume of up to 0.6 cm 3 and mosaic spread of less then 0.4 0 . (orig.) [de

  3. High-temperature Raman study of L-alanine, L-threonine and taurine crystals related to thermal decomposition

    International Nuclear Information System (INIS)

    Cavaignac, A.L.O.; Lima, R.J.C.; Façanha Filho, P.F.; Moreno, A.J.D.; Freire, P.T.C.

    2016-01-01

    In this work high-temperature Raman spectra are used to compare temperature dependence of the lattice mode wavenumber of L-alanine, L-threonine and taurine crystals. Anharmonic effects observed are associated with intermolecular N-H· · ·O hydrogen bond that plays an important role in thermal decomposition process of these materials. Short and strong hydrogen bonds in L-alanine crystal were associated with anharmonic effects in lattice modes leading to low thermal stability compared to taurine crystals. Connection between thermal decomposition process and anharmonic effects is furnished for the first time.

  4. High-temperature Raman study of L-alanine, L-threonine and taurine crystals related to thermal decomposition

    Science.gov (United States)

    Cavaignac, A. L. O.; Lima, R. J. C.; Façanha Filho, P. F.; Moreno, A. J. D.; Freire, P. T. C.

    2016-03-01

    In this work high-temperature Raman spectra are used to compare temperature dependence of the lattice mode wavenumber of L-alanine, L-threonine and taurine crystals. Anharmonic effects observed are associated with intermolecular N-H· · ·O hydrogen bond that plays an important role in thermal decomposition process of these materials. Short and strong hydrogen bonds in L-alanine crystal were associated with anharmonic effects in lattice modes leading to low thermal stability compared to taurine crystals. Connection between thermal decomposition process and anharmonic effects is furnished for the first time.

  5. Mesoscopic self-collimation and slow light in all-positive index layered photonic crystals.

    Science.gov (United States)

    Arlandis, Julien; Centeno, Emmanuel; Pollès, Rémi; Moreau, Antoine; Campos, Julien; Gauthier-Lafaye, Olivier; Monmayrant, Antoine

    2012-01-20

    We demonstrate a mesoscopic self-collimation effect in photonic crystal superlattices consisting of a periodic set of all-positive index 2D photonic crystal and homogeneous layers. We develop an electromagnetic theory showing that diffraction-free beams are observed when the curvature of the optical dispersion relation is properly compensated for. This approach allows us to combine slow-light regime together with self-collimation in photonic crystal superlattices presenting an extremely low filling ratio in air. © 2012 American Physical Society

  6. Controlling Anderson localization in disordered photonic crystal waveguides

    DEFF Research Database (Denmark)

    Smolka, Stephan; Garcia, Pedro D.; Lodahl, Peter

    2010-01-01

    We prove Anderson localization in the slow-light regime of a photonic crystal waveguide by measuring the ensemble-averaged localization length which is controlled by the dispersion of the disordered photonic crystal waveguide.......We prove Anderson localization in the slow-light regime of a photonic crystal waveguide by measuring the ensemble-averaged localization length which is controlled by the dispersion of the disordered photonic crystal waveguide....

  7. Emergence of Zeolite Analogs and other Microporous Crystals in an Atomic Lattice Model of Silica and Related Materials.

    Science.gov (United States)

    Jin, Lin; Auerbach, Scott M; Monson, Peter A

    2012-03-15

    The potential of tailored nanopores to transform technologies such as drug delivery, biofuel production, and optical-electronic devices depends on fundamental knowledge of the self-assembly of ordered nanoporous solids. Atomic-level geometries of critical nuclei that lead to such solids have remained hidden in the nanoscale blind spot between local (5 nm) probes of structure. Heroic efforts at molecular simulation of nanopore formation have provided massive libraries of hypothetical structures; (1-5) however, to date no statistical simulation has generated a crystallization pathway from random initial condition to ordered nanoporous solid, until now. In this work, we show that a recently developed atomic lattice model of silica and related materials can form ordered nanoporous solids with a rich variety of structures including known chalcogenides, zeolite analogs, and layered materials. We find that whereas canonical Monte Carlo simulations of the model consistently produce the amorphous solids studied in our previous work, parallel tempering Monte Carlo gives rise to ordered nanoporous solids. The utility of parallel tempering highlights the existence of barriers between amorphous and crystalline phases of our model. Moreover, the self-assembly or nanoporous crystalline phases in the model open the door to detailed understanding of nanopore nucleation.

  8. EMR-related problems at the interface between the crystal field Hamiltonians and the zero-field splitting Hamiltonians

    Directory of Open Access Journals (Sweden)

    Rudowicz Czesław

    2015-07-01

    Full Text Available The interface between optical spectroscopy, electron magnetic resonance (EMR, and magnetism of transition ions forms the intricate web of interrelated notions. Major notions are the physical Hamiltonians, which include the crystal field (CF (or equivalently ligand field (LF Hamiltonians, and the effective spin Hamiltonians (SH, which include the zero-field splitting (ZFS Hamiltonians as well as to a certain extent also the notion of magnetic anisotropy (MA. Survey of recent literature has revealed that this interface, denoted CF (LF ↔ SH (ZFS, has become dangerously entangled over the years. The same notion is referred to by three names that are not synonymous: CF (LF, SH (ZFS, and MA. In view of the strong need for systematization of nomenclature aimed at bringing order to the multitude of different Hamiltonians and the associated quantities, we have embarked on this systematization. In this article, we do an overview of our efforts aimed at providing a deeper understanding of the major intricacies occurring at the CF (LF ↔ SH (ZFS interface with the focus on the EMR-related problems for transition ions.

  9. Travel-related costs of population dispersion in the provision of domiciliary care to the elderly: a case study in English Local Authorities.

    Science.gov (United States)

    Hindle, Tony; Hindle, Giles; Spollen, Martin

    2009-02-01

    The aim of this research has been to make a contribution to deliberations concerning the relative costs of provision of domiciliary services for the elderly in local authorities in England and the implications for funding. The main services considered have been day-centre services and home-care services, and the particular cost areas investigated have been travel-related costs as associated with distances travelled by day-centre vehicles and care workers and with worker travelling hours. These costs are influenced by the population settlement and dispersion characteristics of the areas served and funding mechanisms are needed (and are in place) to compensate service providers. However, current mechanisms have been widely criticized and the research reported here reaches conclusions about whether such criticisms are justified and how improvements might be brought about. The methods used have involved detailed operational modelling of the selected services in a sample of local authority areas and the generalization of the findings to England as a whole.

  10. Neutron and x-ray scattering study of phonon dispersion and diffuse scattering in (Na ,Bi ) Ti O3-x BaTi O3 single crystals near the morphotropic phase boundary

    Science.gov (United States)

    Luo, Chengtao; Bansal, Dipanshu; Li, Jiefang; Viehland, Dwight; Winn, Barry; Ren, Yang; Li, Xiaobing; Luo, Haosu; Delaire, Olivier

    2017-11-01

    Neutron and x-ray scattering measurements were performed on (N a1 /2B i1 /2 ) Ti O3-x at %BaTi O3 (NBT-x BT ) single crystals (x =4 , 5, 6.5, and 7.5) across the morphotropic phase boundary (MPB), as a function of both composition and temperature, and probing both structural and dynamical aspects. In addition to the known diffuse scattering pattern near the Γ points, our measurements revealed new, faint superlattice peaks, as well as an extensive diffuse scattering network, revealing a short-range ordering of polar nanoregions (PNR) with a static stacking morphology. In samples with compositions closest to the MPB, our inelastic neutron scattering investigations of the phonon dynamics showed two unusual features in the acoustic phonon branches, between the superlattice points, and between the superlattice points and Γ points, respectively. These critical elements are not present in the other compositions away from the MPB, which suggests that these features may be related to the tilt modes coupling behavior near the MPB.

  11. Comprehensive three-dimensional analysis of surface plasmon polariton modes at uniaxial liquid crystal-metal interface.

    Science.gov (United States)

    Yen, Yin-Ray; Lee, Tsun-Hsiun; Wu, Zheng-Yu; Lin, Tsung-Hsien; Hung, Yu-Ju

    2015-12-14

    This paper describes the derivation of surface plasmon polariton modes associated with the generalized three-dimensional rotation of liquid crystal molecules on a metal film. The calculated dispersion relation was verified by coupling laser light into surface plasmon polariton waves in a one-dimensional grating device. The grating-assisted plasmon coupling condition was consistent with the formulated k(spp) value. This provides a general rule for the design of liquid-crystal tunable plasmonic devices.

  12. Turbulent dispersal promotes species coexistence

    Science.gov (United States)

    Berkley, Heather A; Kendall, Bruce E; Mitarai, Satoshi; Siegel, David A

    2010-01-01

    Several recent advances in coexistence theory emphasize the importance of space and dispersal, but focus on average dispersal rates and require spatial heterogeneity, spatio-temporal variability or dispersal-competition tradeoffs to allow coexistence. We analyse a model with stochastic juvenile dispersal (driven by turbulent flow in the coastal ocean) and show that a low-productivity species can coexist with a high-productivity species by having dispersal patterns sufficiently uncorrelated from those of its competitor, even though, on average, dispersal statistics are identical and subsequent demography and competition is spatially homogeneous. This produces a spatial storage effect, with an ephemeral partitioning of a ‘spatial niche’, and is the first demonstration of a physical mechanism for a pure spatiotemporal environmental response. ‘Turbulent coexistence’ is widely applicable to marine species with pelagic larval dispersal and relatively sessile adult life stages (and perhaps some wind-dispersed species) and complements other spatial and temporal storage effects previously documented for such species. PMID:20455921

  13. Accidental degeneracy of double Dirac cones in a phononic crystal

    KAUST Repository

    Chen, Ze-Guo

    2014-04-09

    Artificial honeycomb lattices with Dirac cone dispersion provide a macroscopic platform to study the massless Dirac quasiparticles and their novel geometric phases. In this paper, a quadruple-degenerate state is achieved at the center of the Brillouin zone in a two-dimensional honeycomb lattice phononic crystal, which is a result of accidental degeneracy of two double-degenerate states. In the vicinity of the quadruple-degenerate state, the dispersion relation is linear. Such quadruple degeneracy is analyzed by rigorous representation theory of groups. Using method, a reduced Hamiltonian is obtained to describe the linear Dirac dispersion relations of this quadruple-degenerate state, which is well consistent with the simulation results. Near such accidental degeneracy, we observe some unique properties in wave propagating, such as defect-insensitive propagating character and the Talbot effect.

  14. Crystallization of the receptor-binding domain of parathyroid hormone-related protein in complex with a neutralizing monoclonal antibody Fab fragment

    Energy Technology Data Exchange (ETDEWEB)

    McKinstry, William J.; Polekhina, Galina; Diefenbach-Jagger, Hannelore; Sato, Koh; Onuma, Etsuro; Gillespie, Matthew T.; Martin, Thomas J.; Parker, Michael W.; (SVIMR-A); (Chugai); (Melbourne)

    2009-04-01

    Parathyroid hormone-related protein (PTHrP) plays an important role in regulating embryonic skeletal development and is abnormally regulated in the pathogenesis of skeletal complications observed with many cancers and osteoporosis. It exerts its action through binding to a G-protein-coupled seven-transmembrane cell-surface receptor (GPCR). Structurally, GPCRs are very difficult to study by X-ray crystallography. In this study, a monoclonal antibody Fab fragment which recognizes the same region of PTHrP as its receptor, PTH1R, was used to aid in the crystallization of PTHrP. The resultant protein complex was crystallized using the hanging-drop vapour-diffusion method with polyethylene glycol as a precipitant. The crystals belonged to the orthorhombic space group P2{sub 1}2{sub 1}2, with unit-cell parameters a = 72.6, b = 96.3, c = 88.5 {angstrom}, and diffracted to 2.0 {angstrom} resolution using synchrotron radiation. The crystal structure will shed light on the nature of the key residues of PTHrP that interact with the antibody and will provide insights into how the antibody is able to discriminate between PTHrP and the related molecule parathyroid homone.

  15. Transport of pollutants by gravitational settling of ice crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hauf, T.; Alheit, R. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

    1997-12-01

    A numerical box model was developed which simulates the cloud microphysical development within an air parcel of a developing contrail. In a series of simulations it could be shown that in most cases the effective size of the ice crystals is less than 10 {mu}m. Only for high supersaturation (over ice) in the environment and relatively low supersaturation (over water) within the contrail ice crystals larger than 20 {mu}m develop and fall out of the contrail. The hypothesised related transport of pollutants by gravitational settling of ice crystals, therefore, is an unimportant effect when the large-scale dispersion of aircraft exhausts is considered. (orig.) 144 figs., 42 tabs., 497 refs.

  16. Low-loss and bendable THz fiber with tailored dispersion

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Adam, Aurèle J. L.

    2009-01-01

    A polymer THz fiber made of Topas and having a Photonic Crystal Fiber structure is demonstrated. It has low broadband loss and the dispersion of the fiber can be tailored by adjusting the structural parameters.......A polymer THz fiber made of Topas and having a Photonic Crystal Fiber structure is demonstrated. It has low broadband loss and the dispersion of the fiber can be tailored by adjusting the structural parameters....

  17. Dispersed flow film boiling

    International Nuclear Information System (INIS)

    Andreani, M.; Yadigaroglu, G.

    1989-12-01

    Dispersed flow film boiling is the heat transfer regime that occurs at high void fractions in a heated channel. The way this transfer mode is modelled in the NRC computer codes (RELAP5 and TRAC) and the validity of the assumption and empirical correlations used is discussed. An extensive review of the theoretical and experimental work related with heat transfer to highly dispersed mixtures reveals the basic deficiencies of these models: the investigation refers mostly to the typical conditions of low rate bottom reflooding, since the simulation of this physical situation by the computer codes has often showed poor results. The alternative models that are available in the literature are reviewed, and their merits and limits are highlighted. The modification that could improve the physics of the models implemented in the codes are identified. (author) 13 figs., 123 refs

  18. Direct comparison of shot-to-shot noise performance of all normal dispersion and anomalous dispersion supercontinuum pumped with sub-picosecond pulse fiber-based laser

    Science.gov (United States)

    Klimczak, Mariusz; Soboń, Grzegorz; Kasztelanic, Rafał; Abramski, Krzysztof M.; Buczyński, Ryszard

    2016-01-01

    Coherence of supercontinuum sources is critical for applications involving characterization of ultrafast or rarely occurring phenomena. With the demonstrated spectral coverage of supercontinuum extending from near-infrared to over 10 μm in a single nonlinear fiber, there has been a clear push for the bandwidth rather than for attempting to optimize the dynamic properties of the generated spectrum. In this work we provide an experimental assessment of the shot-to-shot noise performance of supercontinuum generation in two types of soft glass photonic crystal fibers. Phase coherence and intensity fluctuations are compared for the cases of an anomalous dispersion-pumped fiber and an all-normal dispersion fiber. With the use of the dispersive Fourier transformation method, we demonstrate that a factor of 100 improvement in signal-to-noise ratio is achieved in the normal-dispersion over anomalous dispersion-pumped fiber for 390 fs long pump pulses. A double-clad design of the photonic lattice of the fiber is further postulated to enable a pump-related seeding mechanism of normal-dispersion supercontinuum broadening under sub-picosecond pumping, which is otherwise known for similar noise characteristics as modulation instability driven, soliton-based spectra. PMID:26759188

  19. Anti-Transforming Growth Factor β IgG Elicits a Dual Effect on Calcium Oxalate Crystallization and Progressive Nephrocalcinosis-Related Chronic Kidney Disease

    Directory of Open Access Journals (Sweden)

    Stefanie Steiger

    2018-03-01

    Full Text Available Crystallopathies are a heterogeneous group of diseases caused by intrinsic or environmental microparticles or crystals, promoting tissue inflammation and scarring. Certain proteins interfere with crystal formation and growth, e.g., with intrarenal calcium oxalate (CaOx crystal formation, a common cause of kidney stone disease or nephrocalcinosis-related chronic kidney disease (CKD. We hypothesized that immunoglobulins can modulate CaOx microcrystal formation and crystal growth and that therefore, biological IgG-based drugs designed to specifically target disease modifying proteins would elicit a dual effect on the outcome of CaOx-related crystallopathies. Indeed, both the anti-transforming growth factor (TGFβ IgG and control IgG1 antibody impaired CaOx crystallization in vitro, and decreased intrarenal CaOx crystal deposition and subsequent CKD in mice on an oxalate-rich diet compared to oxalate-fed control mice. However, the TGFβ-specific IgG antibody showed nephroprotective effects beyond those of control IgG1 and substantially reduced interstitial fibrosis as indicated by magnetic resonance imaging, silver and α-smooth muscle actin staining, RT-qPCR, and flow cytometry for pro-fibrotic macrophages. Suppressing interstitial fibrosis slowed the decline of glomerular filtration rate (GFR compared to treatment with control IgG1 [slope of m = −8.9 vs. m = −14.5 μl/min/100 g body weight (BW/day, Δ = 38.3%], an increased GFR at the end of the study (120.4 vs. 42.6 μl/min/100 g BW, Δ = 64.6%, and prolonged end stage renal disease (ESRD-free renal survival by 10 days (Δ = 38.5%. Delayed onset of anti-TGFβ IgG from day 7 was no longer effective. Our results suggest that biological drugs can elicit dual therapeutic effects on intrinsic crystallopathies, such as anti-TGFβ IgG antibody treatment inhibits CaOx crystallization as well as interstitial fibrosis in nephrocalcinosis-related CKD.

  20. Anti-Transforming Growth Factor β IgG Elicits a Dual Effect on Calcium Oxalate Crystallization and Progressive Nephrocalcinosis-Related Chronic Kidney Disease.

    Science.gov (United States)

    Steiger, Stefanie; Grill, Julia Felicitas; Ma, Qiuyue; Bäuerle, Tobias; Jordan, Jutta; Smolle, Michaela; Böhland, Claudia; Lech, Maciej; Anders, Hans-Joachim

    2018-01-01

    Crystallopathies are a heterogeneous group of diseases caused by intrinsic or environmental microparticles or crystals, promoting tissue inflammation and scarring. Certain proteins interfere with crystal formation and growth, e.g., with intrarenal calcium oxalate (CaOx) crystal formation, a common cause of kidney stone disease or nephrocalcinosis-related chronic kidney disease (CKD). We hypothesized that immunoglobulins can modulate CaOx microcrystal formation and crystal growth and that therefore, biological IgG-based drugs designed to specifically target disease modifying proteins would elicit a dual effect on the outcome of CaOx-related crystallopathies. Indeed, both the anti-transforming growth factor (TGF)β IgG and control IgG1 antibody impaired CaOx crystallization in vitro , and decreased intrarenal CaOx crystal deposition and subsequent CKD in mice on an oxalate-rich diet compared to oxalate-fed control mice. However, the TGFβ-specific IgG antibody showed nephroprotective effects beyond those of control IgG1 and substantially reduced interstitial fibrosis as indicated by magnetic resonance imaging, silver and α-smooth muscle actin staining, RT-qPCR, and flow cytometry for pro-fibrotic macrophages. Suppressing interstitial fibrosis slowed the decline of glomerular filtration rate (GFR) compared to treatment with control IgG1 [slope of m  = -8.9 vs. m  = -14.5 μl/min/100 g body weight (BW)/day, Δ = 38.3%], an increased GFR at the end of the study (120.4 vs. 42.6 μl/min/100 g BW, Δ = 64.6%), and prolonged end stage renal disease (ESRD)-free renal survival by 10 days (Δ = 38.5%). Delayed onset of anti-TGFβ IgG from day 7 was no longer effective. Our results suggest that biological drugs can elicit dual therapeutic effects on intrinsic crystallopathies, such as anti-TGFβ IgG antibody treatment inhibits CaOx crystallization as well as interstitial fibrosis in nephrocalcinosis-related CKD.

  1. Nematic Liquid-Crystal Colloids.

    Science.gov (United States)

    Muševič, Igor

    2017-12-25

    This article provides a concise review of a new state of colloidal matter called nematic liquid-crystal colloids. These colloids are obtained by dispersing microparticles of different shapes in a nematic liquid crystal that acts as a solvent for the dispersed particles. The microparticles induce a local deformation of the liquid crystal, which then generates topological defects and long-range forces between the neighboring particles. The colloidal forces in nematic colloids are much stronger than the forces in ordinary colloids in isotropic solvents, exceeding thousands of k B T per micrometer-sized particle. Of special interest are the topological defects in nematic colloids, which appear in many fascinating forms, such as singular points, closed loops, multitudes of interlinked and knotted loops or soliton-like structures. The richness of the topological phenomena and the possibility to design and control topological defects with laser tweezers make colloids in nematic liquid crystals an excellent playground for testing the basic theorems of topology.

  2. Taylor dispersion of nanoparticles

    Science.gov (United States)

    Balog, Sandor; Urban, Dominic A.; Milosevic, Ana M.; Crippa, Federica; Rothen-Rutishauser, Barbara; Petri-Fink, Alke

    2017-08-01

    The ability to detect and accurately characterize particles is required by many fields of nanotechnology, including materials science, nanotoxicology, and nanomedicine. Among the most relevant physicochemical properties of nanoparticles, size and the related surface-to-volume ratio are fundamental ones. Taylor dispersion combines three independent phenomena to determine particle size: optical extinction, translational diffusion, and sheer-enhanced dispersion of nanoparticles subjected to a steady laminar flow. The interplay of these defines the apparent size. Considering that particles in fact are never truly uniform nor monodisperse, we rigorously address particle polydispersity and calculate the apparent particle size measured by Taylor dispersion analysis. We conducted case studies addressing aqueous suspensions of model particles and large-scale-produced "industrial" particles of both academic and commercial interest of various core materials and sizes, ranging from 15 to 100 nm. A comparison with particle sizes determined by transmission electron microscopy confirms that our approach is model-independent, non-parametric, and of general validity that provides an accurate account of size polydispersity—independently on the shape of the size distribution and without any assumption required a priori.

  3. Peruvians Dispersed

    DEFF Research Database (Denmark)

    Pærregaard, Karsten

    into the receiving societies and achieve physical and social mobility, 2) to explore how the experience of migration and adaptation to their new countries of residence transforms Peruvians’ own ideas of class, nationality, ethnicity and regionality, and 3) to use the Peruvian material to discuss more general aspects...... processes, and economic and social ties with Peru.  On the other hand, it explores the comparative dimension of Peruvian migration by locating the ethnographic in-depth studies of particular migrant communities in Spain, the United States, Japan and Argentina within a broader economic and political context.  ......This book presents a comparative study of Peruvian transnational migration to the United States, Spain, Japan and Argentina. It applies a multi-sited ethnographic fieldwork approach to study is the multicultural life-world of Peruvians and the economic, social, political and ritual relations...

  4. Aspects of numerical and representational methods related to the finite-difference simulation of advective and dispersive transport of freshwater in a thin brackish aquifer

    Science.gov (United States)

    Merritt, M.L.

    1993-01-01

    The simulation of the transport of injected freshwater in a thin brackish aquifer, overlain and underlain by confining layers containing more saline water, is shown to be influenced by the choice of the finite-difference approximation method, the algorithm for representing vertical advective and dispersive fluxes, and the values assigned to parametric coefficients that specify the degree of vertical dispersion and molecular diffusion that occurs. Computed potable water recovery efficiencies will differ depending upon the choice of algorithm and approximation method, as will dispersion coefficients estimated based on the calibration of simulations to match measured data. A comparison of centered and backward finite-difference approximation methods shows that substantially different transition zones between injected and native waters are depicted by the different methods, and computed recovery efficiencies vary greatly. Standard and experimental algorithms and a variety of values for molecular diffusivity, transverse dispersivity, and vertical scaling factor were compared in simulations of freshwater storage in a thin brackish aquifer. Computed recovery efficiencies vary considerably, and appreciable differences are observed in the distribution of injected freshwater in the various cases tested. The results demonstrate both a qualitatively different description of transport using the experimental algorithms and the interrelated influences of molecular diffusion and transverse dispersion on simulated recovery efficiency. When simulating natural aquifer flow in cross-section, flushing of the aquifer occurred for all tested coefficient choices using both standard and experimental algorithms. ?? 1993.

  5. Frequency doubling crystals

    Science.gov (United States)

    Wang, Francis; Velsko, Stephan P.

    1989-01-01

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  6. Determination of residual acetone and acetone related impurities in drug product intermediates prepared as Spray Dried Dispersions (SDD) using gas chromatography with headspace autosampling (GCHS).

    Science.gov (United States)

    Quirk, Emma; Doggett, Adrian; Bretnall, Alison

    2014-08-05

    Spray Dried Dispersions (SDD) are uniform mixtures of a specific ratio of amorphous active pharmaceutical ingredient (API) and polymer prepared via a spray drying process. Volatile solvents are employed during spray drying to facilitate the formation of the SDD material. Following manufacture, analytical methodology is required to determine residual levels of the spray drying solvent and its associated impurities. Due to the high level of polymer in the SDD samples, direct liquid injection with Gas Chromatography (GC) is not a viable option for analysis. This work describes the development and validation of an analytical approach to determine residual levels of acetone and acetone related impurities, mesityl oxide (MO) and diacetone alcohol (DAA), in drug product intermediates prepared as SDDs using GC with headspace (HS) autosampling. The method development for these analytes presented a number of analytical challenges which had to be overcome before the levels of the volatiles of interest could be accurately quantified. GCHS could be used after two critical factors were implemented; (1) calculation and application of conversion factors to 'correct' for the reactions occurring between acetone, MO and DAA during generation of the headspace volume for analysis, and the addition of an equivalent amount of polymer into all reference solutions used for quantitation to ensure comparability between the headspace volumes generated for both samples and external standards. This work describes the method development and optimisation of the standard preparation, the headspace autosampler operating parameters and the chromatographic conditions, together with a summary of the validation of the methodology. The approach has been demonstrated to be robust and suitable to accurately determine levels of acetone, MO and DAA in SDD materials over the linear concentration range 0.008-0.4μL/mL, with minimum quantitation limits of 20ppm for acetone and MO, and 80ppm for DAA. Copyright

  7. Tamm-plasmon polaritons in one-dimensional photonic quasi-crystals.

    Science.gov (United States)

    Shukla, Mukesh Kumar; Das, Ritwick

    2018-02-01

    We present an investigation to ascertain the existence of Tamm-plasmon-polariton-like modes in one-dimensional (1D) quasi-periodic photonic systems. Photonic bandgap formation in quasi-crystals is essentially a consequence of long-range periodicity exhibited by multilayers and, thus, it can be explained using the dispersion relation in the Brillouin zone. Defining a "Zak"-like topological phase in 1D quasi-crystals, we propose a recipe to ascertain the existence of Tamm-like photonic surface modes in a metal-terminated quasi-crystal lattice. Additionally, we also explore the conditions of efficient excitation of such surface modes along with their dispersion characteristics.

  8. Relative neutronic performance of proposed high-density dispersion fuels in water-moderated and D2O-reflected research reactors

    International Nuclear Information System (INIS)

    Bretscher, M.M.; Matos, J.E.; Snelgrove, J.L.

    1996-01-01

    This paper provides an overview of the neutronic performance of an idealized research reactor using several high density LEU fuels that are being developed by the RERTR program. High-density LEU dispersion fuels are needed for new and existing high-performance research reactors and to extend the lifetime of fuel elements in other research reactors. This paper discusses the anticipated neutronic behavior of proposed advanced fuels containing dispersions of U 3 Si 2 , UN, U 2 Mo and several uranium alloys with Mo, or Zr and Nb. These advanced fuels are ranked based on the results of equilibrium depletion calculations for a simplified reactor model having a small H 2 O-cooled core and a D 2 O reflector. Plans have been developed to fabricate and irradiate several uranium alloy dispersion fuels in order to test their stability and compatibility with the matrix material and to establish practical loading limits

  9. Relative neutronic performance of proposed high-density dispersion fuels in water-moderated and D2O-reflected research reactors

    International Nuclear Information System (INIS)

    Bretscher, M.M.; Matos, J.E.; Snelgrove, J.L.

    1996-01-01

    This paper provides an overview of the neutronic performance of an idealized research reactor using several high density Leu fuels that are being developed by the Rarita program. High-density Leu dispersion fuels are needed for new and existing high-performance research reactors and to extend the lifetime of fuel elements in other research reactors. This paper discusses the anticipated neutronic behavior of proposed advanced fuels containing dispersions of U 3 Si 2 , UN, U 2 Mo and several uranium alloys with Mo, or Zr and Nb. These advanced fuels are ranked based on the results of equilibrium depletion calculations for a simplified reactor model having a small H 2 O-cooled core and a D 2 O reflector. Plans have been developed to fabricate and irradiate several uranium alloy dispersion fuels in order to test their stability and compatibility with the matrix material and to establish practical loading limits. (author)

  10. Band structure and optical properties of diglycine nitrate crystal

    International Nuclear Information System (INIS)

    Andriyevsky, Bohdan; Ciepluch-Trojanek, Wioleta; Romanyuk, Mykola; Patryn, Aleksy; Jaskolski, Marcin

    2005-01-01

    Experimental and theoretical investigations of the electron energy characteristics and optical spectra for diglycine nitrate crystal (DGN) (NH 2 CH 2 COOH) 2 .HNO 3 , in the paraelectric phase (T=295K) are presented. Spectral dispersion of light reflection R(E) have been measured in the range of 3-22eV and the optical functions n(E) and k(E) have been calculated using Kramers-Kronig relations. First principal calculations of the electron energy characteristic and optical spectra of DGN crystal have been performed in the frame of density functional theory using CASTEP code (CAmbridge Serial Total Energy Package). Optical transitions forming the low-energy edge of fundamental absorption are associated with the nitrate groups NO 3 . Peculiarities of the band structure and DOS projected onto glycine and NO 3 groups confirm the molecular character of DGN crystal

  11. Theoretical analysis of a biased photonic crystal fiber infiltrated with a negative dielectric anisotropy liquid crystal

    DEFF Research Database (Denmark)

    Weirich, Johannes; Wei, Lei; Lægsgaard, Jesper

    2009-01-01

    We simulate the PBG mode of a biased Photonic Crystal Fiber (PCF) infiltrated with a Liquid Crystal (LC) with negative dielectric anisotropy. We analyse the voltage induced change of the transmission spectrum, dispersion and losses and compare them to the experimental values.......We simulate the PBG mode of a biased Photonic Crystal Fiber (PCF) infiltrated with a Liquid Crystal (LC) with negative dielectric anisotropy. We analyse the voltage induced change of the transmission spectrum, dispersion and losses and compare them to the experimental values....

  12. Investigation of growth rate dispersion in lactose crystallisation by AFM

    Science.gov (United States)

    Dincer, T. D.; Ogden, M. I.; Parkinson, G. M.

    2014-09-01

    α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (0 1 0) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (0 1 0) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (0 1 0) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the (c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.

  13. Quadrupolar interactions in non-cubic crystal and related extra heat capacities. Possible effects on a sapphire bolometer

    Energy Technology Data Exchange (ETDEWEB)

    Bassou, M. [Tunis Univ. (Tunisia)]|[CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Rotter, M. [Karlova Univ., Prague (Czech Republic)]|[CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Bernier, M. [CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Chapellier, M. [CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France)

    1996-02-11

    It is shown that in a non-cubic crystal, the extra heat capacity due to quadrupolar interaction of nuclear spins >1/2 could be much bigger than the phonon heat capacity when the temperature decreases. The possible coupling between quadrupolar and phonon heat reservoir via paramagnetic impurities is stressed. A NMR experiment done on sapphire is presented with an evaluation of the coupling between the two reservoirs and its consequence on the performance of the bolometer. (orig.).

  14. Quadrupolar interactions in non-cubic crystal and related extra heat capacities. Possible effects on a sapphire bolometer

    International Nuclear Information System (INIS)

    Bassou, M.; Rotter, M.; Bernier, M.; Chapellier, M.

    1996-01-01

    It is shown that in a non-cubic crystal, the extra heat capacity due to quadrupolar interaction of nuclear spins >1/2 could be much bigger than the phonon heat capacity when the temperature decreases. The possible coupling between quadrupolar and phonon heat reservoir via paramagnetic impurities is stressed. A NMR experiment done on sapphire is presented with an evaluation of the coupling between the two reservoirs and its consequence on the performance of the bolometer. (orig.)

  15. Relaxor properties of barium titanate crystals grown by Remeika method

    Science.gov (United States)

    Roth, Michel; Tiagunov, Jenia; Dul'kin, Evgeniy; Mojaev, Evgeny

    2017-06-01

    Barium titanate (BaTiO3, BT) crystals have been grown by the Remeika method using both the regular KF and mixed KF-NaF (0.6-0.4) solvents. Typical acute angle "butterfly wing" BT crystals have been obtained, and they were characterized using x-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy), conventional dielectric and acoustic emission methods. A typical wing has a triangular plate shape which is up to 0.5 mm thick with a 10-15 mm2 area. The plate has a (001) habit and an atomically smooth outer surface. Both K+ and F- solvent ions are incorporated as dopants into the crystal lattice during growth substituting for Ba2+ and O2- ions respectively. The dopants' distribution is found to be inhomogeneous, their content being almost an order of magnitude higher (up to 2 mol%) at out surface of the plate relatively to the bulk. A few μm thick surface layer is formed where a multidomain ferroelectric net is confined between two≤1 μm thick dopant-rich surfaces. The layer as a whole possess relaxor ferroelectric properties, which is apparent from the appearance of additional broad maxima, Tm, in the temperature dependence of the dielectric permittivity around the ferroelectric phase transition. Intense acoustic emission responses detected at temperatures corresponding to the Tm values allow to observe the Tm shift to lower temperatures at higher frequencies, or dispersion, typical for relaxor ferroelectrics. The outer surface of the BT wing can thus serve as a relaxor thin film for various electronic application, such as capacitors, or as a substrate for BT-based multiferroic structure. Crystals grown from KF-NaF fluxes contain sodium atoms as an additional impurity, but the crystal yield is much smaller, and while the ferroelectric transition peak is diffuse it does not show any sign of dispersion typical for relaxor behavior.

  16. Global dispersal pattern of HIV type 1 subtype CRF01-AE : A genetic trace of human mobility related to heterosexual sexual activities centralized in southeast Asia

    NARCIS (Netherlands)

    Angelis, Konstantinos; Albert, Jan; Mamais, Ioannis; Magiorkinis, Gkikas; Hatzakis, Angelos; Hamouda, Osamah; Struck, Daniel; Vercauteren, Jurgen; Wensing, Annemarie M J; Alexiev, Ivailo; Åsjö, Birgitta; Balotta, Claudia; Camacho, Ricardo J.; Coughlan, Suzie; Griskevicius, Algirdas; Grossman, Zehava; Horban, Andrzej; Kostrikis, Leondios G.; Lepej, Snjezana; Liitsola, Kirsi; Linka, Marek; Nielsen, Claus; Otelea, Dan; Paredes, Roger; Poljak, Mario; Puchhammer-Stöckl, Elisabeth; Schmit, Jean Claude; Sönnerborg, Anders; Staneková, Danica; Stanojevic, Maja; Boucher, Charles A B; Kaplan, Lauren; Vandamme, Anne Mieke; Paraskevis, Dimitrios

    2015-01-01

    Background. Human immunodeficiency virus type 1 (HIV-1) subtype CRF01-AE originated in Africa and then passed to Thailand, where it established a major epidemic. Despite the global presence of CRF01-AE, little is known about its subsequent dispersal pattern. Methods. We assembled a global data set

  17. Global Dispersal Pattern of HIV Type 1 Subtype CRF01_AE: A Genetic Trace of Human Mobility Related to Heterosexual Sexual Activities Centralized in Southeast Asia.

    Science.gov (United States)

    Angelis, Konstantinos; Albert, Jan; Mamais, Ioannis; Magiorkinis, Gkikas; Hatzakis, Angelos; Hamouda, Osamah; Struck, Daniel; Vercauteren, Jurgen; Wensing, Annemarie M J; Alexiev, Ivailo; Åsjö, Birgitta; Balotta, Claudia; Camacho, Ricardo J; Coughlan, Suzie; Griskevicius, Algirdas; Grossman, Zehava; Horban, Andrzej; Kostrikis, Leondios G; Lepej, Snjezana; Liitsola, Kirsi; Linka, Marek; Nielsen, Claus; Otelea, Dan; Paredes, Roger; Poljak, Mario; Puchhammer-Stöckl, Elisabeth; Schmit, Jean-Claude; Sönnerborg, Anders; Staneková, Danica; Stanojevic, Maja; Boucher, Charles A B; Kaplan, Lauren; Vandamme, Anne-Mieke; Paraskevis, Dimitrios

    2015-06-01

    Human immunodeficiency virus type 1 (HIV-1) subtype CRF01_AE originated in Africa and then passed to Thailand, where it established a major epidemic. Despite the global presence of CRF01_AE, little is known about its subsequent dispersal pattern. We assembled a global data set of 2736 CRF01_AE sequences by pooling sequences from public databases and patient-cohort studies. We estimated viral dispersal patterns, using statistical phylogeographic analysis run over bootstrap trees estimated by the maximum likelihood method. We show that Thailand has been the source of viral dispersal to most areas worldwide, including 17 of 20 sampled countries in Europe. Japan, Singapore, Vietnam, and other Asian countries have played a secondary role in the viral dissemination. In contrast, China and Taiwan have mainly imported strains from neighboring Asian countries, North America, and Africa without any significant viral exportation. The central role of Thailand in the global spread of CRF01_AE can be probably explained by the popularity of Thailand as a vacation destination characterized by sex tourism and by Thai emigration to the Western world. Our study highlights the unique case of CRF01_AE, the only globally distributed non-B clade whose global dispersal did not originate in Africa. © The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  18. Parentage analysis of Ansell’s mole-rat family groups indicates a high reproductive skew despite relatively relaxed ecological constraints on dispersal

    Czech Academy of Sciences Publication Activity Database

    Patzenhauerová, Hana; Šklíba, J.; Bryja, Josef; Šumbera, R.

    2013-01-01

    Roč. 22, č. 19 (2013), s. 4988-5000 ISSN 0962-1083 R&D Projects: GA AV ČR IAA601410802; GA ČR GAP506/10/0983 Institutional support: RVO:68081766 Keywords : African mole-rat * dispersal * eusociality * Fukomys * mating system * reproductive skew Subject RIV: EH - Ecology, Behaviour Impact factor: 5.840, year: 2013

  19. Crystallization and preliminary X-ray analysis of Na-ASP-1, a multi-domain pathogenesis-related-1 protein from the human hookworm parasite Necator americanus

    Energy Technology Data Exchange (ETDEWEB)

    Asojo, Oluwatoyin A., E-mail: oasojo@unmc.edu [Eppley Institute for Research in Cancer and Allied Diseases, 987696 Nebraska Medical Center, Omaha, NE 68198-7696 (United States); Loukas, Alex [Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington DC 20037 (United States); Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, Brisbane, QLD 4006 (Australia); Inan, Mehmet; Barent, Rick; Huang, Jicai; Plantz, Brad; Swanson, Amber; Gouthro, Mark; Meagher, Michael M. [Department of Chemical Engineering, The University of Nebraska-Lincoln, Lincoln, NE 68588-0643 (United States); Hotez, Peter J. [Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington DC 20037 (United States); Eppley Institute for Research in Cancer and Allied Diseases, 987696 Nebraska Medical Center, Omaha, NE 68198-7696 (United States)

    2005-04-01

    In order to clarify the structural basis of the pathogenesis-related-1 domain, Na-ASP-1, the first multi-domain ASP from the human hookworm parasite N. americanus, has been crystallized. 2.2 Å resolution data have been collected from a crystal belonging to the monoclinic space group P2{sub 1}. Human hookworm infection is a major cause of anemia and malnutrition in the developing world. In an effort to control hookworm infection, the Human Hookworm Vaccine Initiative has identified candidate vaccine antigens from the infective larval stage (L3) of the parasite, including a family of pathogenesis-related-1 (PR-1) proteins known as the ancylostoma-secreted proteins (ASPs). The functions of the ASPs are unknown. In addition, it is unclear why some ASPs have one while others have multiple PR-1 domains. There are no known structures of a multi-domain ASP and in an effort to remedy this situation, recombinant Na-ASP-1 has been expressed, purified and crystallized. Na-ASP-1 is a 406-amino-acid multi-domain ASP from the prevalent human hookworm parasite Necator americanus. Useful X-ray data to 2.2 Å have been collected from a crystal that belongs to the monoclinic space group P2{sub 1} with unit-cell parameters a = 67.7, b = 74.27, c = 84.60 Å, β = 112.12°. An initial molecular-replacement solution has been obtained with one monomer in the asymmetric unit.

  20. Prediction of molecular crystal structures

    CERN Document Server

    Beyer, T

    2001-01-01

    The ab initio prediction of molecular crystal structures is a scientific challenge. Reliability of first-principle prediction calculations would show a fundamental understanding of crystallisation. Crystal structure prediction is also of considerable practical importance as different crystalline arrangements of the same molecule in the solid state (polymorphs)are likely to have different physical properties. A method of crystal structure prediction based on lattice energy minimisation has been developed in this work. The choice of the intermolecular potential and of the molecular model is crucial for the results of such studies and both of these criteria have been investigated. An empirical atom-atom repulsion-dispersion potential for carboxylic acids has been derived and applied in a crystal structure prediction study of formic, benzoic and the polymorphic system of tetrolic acid. As many experimental crystal structure determinations at different temperatures are available for the polymorphic system of parac...

  1. Mid-infrared spectroscopy as a polymer selection tool for formulating amorphous solid dispersions.

    Science.gov (United States)

    Wegiel, Lindsay A; Mauer, Lisa J; Edgar, Kevin J; Taylor, Lynne S

    2014-02-01

    The development of amorphous solid dispersions is of increasing interest in the delivery of bioactive compounds; however, there is a need for a methodology that enables the rational selection of polymers for solid dispersion formulations with optimal stability to crystallization. The objective of this study was to evaluate the use of mid-infrared (IR) spectroscopy for this purpose. Polymers evaluated included poly(vinylpyrrolidone) (PVP), Eudragit E100 (E100), carboxymethylcellulose acetate butyrate (CMCAB), hydroxypropylmethylcellulose (HPMC), HPMC acetate succinate (HPMCAS) and poly(acrylic acid) (PAA). Model crystalline bioactive polyphenols included quercetin and naringenin. Amorphous solid dispersions were prepared by dissolving both polyphenol and polymer in a common solvent followed by solvent evaporation. Mid-IR spectroscopy was used to determine and quantify the extent of polyphenol-polymer interactions, and powder X-ray diffraction was used to monitor physical stability following storage at different environmental conditions. The mid-IR analysis suggested the following rank order for the crystallization-inhibiting performance of the different polymers: E100 > PVP > HPMCAS > HPMC ≥ CMCAB > PAA. The initial performance of the different polymers was evaluated using the highest concentration of polyphenol for which x-ray amorphous solid dispersions could be prepared via rotary evaporation. The observed stability followed that predicted from the mid-infrared spectroscopy evaluation of intermolecular interactions. The dispersions with better polyphenol-polymer interactions were stable against crystallization when exposed to high relative humidity and high temperatures; on the other hand, systems that had weak interactions were not stable to crystallization when stored at moderate environmental conditions. Based on the observed ability of mid-IR analysis to enable the characterization of intermolecular polyphenol-polymer interactions and

  2. Crystal Systems.

    Science.gov (United States)

    Schomaker, Verner; Lingafelter, E. C.

    1985-01-01

    Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

  3. Virtual Crystallizer

    Energy Technology Data Exchange (ETDEWEB)

    Land, T A; Dylla-Spears, R; Thorsness, C B

    2006-08-29

    Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

  4. Crystal Engineering

    Indian Academy of Sciences (India)

    Nangia (2002). “Today, research areas under the wide umbrella of crystal engineering include: supramolecular synthesis; nanotechnology; separation science and catalysis; supramolecular materials and devices; polymorphism; cocrystals, crystal structure prediction; drug design and ligand–protein binding.”

  5. Applications of biomaterials to liquid crystals.

    Science.gov (United States)

    Iwabata, Kazuki; Sugai, Urara; Seki, Yasutaka; Furue, Hirokazu; Sakaguchi, Kengo

    2013-04-19

    Nowadays, chemically synthesized proteins and peptides are attractive building blocks and have potential in many important applications as biomaterials. In this review, applications of biomaterials to thermotropic liquid crystals are discussed. The review covers the improvement of the performance of liquid crystal displays using liquid crystal physical gels consisting of a liquid crystal and amino acid-based gelators, and also new functionalization of liquid crystals. Moreover, the influence of DNA, which is one of the more attractive biomaterials, dispersed in thermotropic liquid crystals and its potential use in the liquid crystal industry is described. In addition, we found interesting results during electrooptical measurements of liquid crystals doped with DNA, and explain them from the point of view of biological applications. These recent approaches suggest that these biomaterials may be applicable in the electronic device industry and should be considered as an interesting material with their physical properties having the potential to create or refine an industrial product.

  6. Applications of Biomaterials to Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Kengo Sakaguchi

    2013-04-01

    Full Text Available Nowadays, chemically synthesized proteins and peptides are attractive building blocks and have potential in many important applications as biomaterials. In this review, applications of biomaterials to thermotropic liquid crystals are discussed. The review covers the improvement of the performance of liquid crystal displays using liquid crystal physical gels consisting of a liquid crystal and amino acid-based gelators, and also new functionalization of liquid crystals. Moreover, the influence of DNA, which is one of the more attractive biomaterials, dispersed in thermotropic liquid crystals and its potential use in the liquid crystal industry is described. In addition, we found interesting results during electrooptical measurements of liquid crystals doped with DNA, and explain them from the point of view of biological applications. These recent approaches suggest that these biomaterials may be applicable in the electronic device industry and should be considered as an interesting material with their physical properties having the potential to create or refine an industrial product.

  7. Dispersion cancellation in a triple Laue interferometer

    International Nuclear Information System (INIS)

    Lemmel, Hartmut

    2014-01-01

    The concept of dispersion cancellation has been established in light optics to improve the resolution of interferometric measurements on dispersive media. Odd order dispersion cancellation allows to measure phase shifts without defocusing the interferometer due to wave packet displacements, while even order dispersion cancellation allows to measure time lags without losing resolution due to wave packet spreading. We report that either type of dispersion cancellation can be realized very easily in a triple Laue interferometer. Such interferometers are Mach–Zehnder interferometers based on Bragg diffraction, and are commonly used for neutrons and x-rays. Although the first x-ray interferometer was built nearly five decades ago, the feature of dispersion cancellation hasn't been recognized so far because the concept was hardly known in the neutron and x-ray community. However, it explains right away the surprising decoupling of phase shift and spatial displacement that we have discovered recently in neutron interferometry (Lemmel and Wagh 2010 Phys. Rev. A 82 033626). Furthermore, this article might inspire the light optics community to consider whether a triple Laue interferometer for laser light would be useful and feasible. We explain how dispersion cancellation works in neutron interferometry, and we describe the setup rigorously by solving the Schrödinger equation and by calculating the path integral. We point out, that the latter has to be evaluated with special care since in our setup the beam trajectory moves with respect to the crystal lattice of the interferometer. (paper)

  8. Dispersing powders in liquids

    CERN Document Server

    Nelson, RD

    1988-01-01

    This book provides powder technologists with laboratory procedures for selecting dispersing agents and preparing stable dispersions that can then be used in particle size characterization instruments. Its broader goal is to introduce industrial chemists and engineers to the phenomena, terminology, physical principles, and chemical considerations involved in preparing and handling dispersions on a commercial scale. The book introduces novices to: - industrial problems due to improper degree of dispersion; - the nomenclature used in describing particles; - the basic physica

  9. Growth of single crystals of BaFe12O19 by solid state crystal growth

    Science.gov (United States)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-10-01

    Single crystals of BaFe12O19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe12O19 are buried in BaFe12O19+1 wt% BaCO3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe12O19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe12O19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth.

  10. Controlled growth of semiconductor crystals

    Science.gov (United States)

    Bourret-Courchesne, Edith D.

    1992-01-01

    A method for growth of III-V, II-VI and related semiconductor single crystals that suppresses random nucleation and sticking of the semiconductor melt at the crucible walls. Small pieces of an oxide of boron B.sub.x O.sub.y are dispersed throughout the comminuted solid semiconductor charge in the crucible, with the oxide of boron preferably having water content of at least 600 ppm. The crucible temperature is first raised to a temperature greater than the melt temperature T.sub.m1 of the oxide of boron (T.sub.m1 =723.degree. K. for boron oxide B.sub.2 O.sub.3), and the oxide of boron is allowed to melt and form a reasonably uniform liquid layer between the crucible walls and bottom surfaces and the still-solid semiconductor charge. The temperature is then raised to approximately the melt temperature T.sub.m2 of the semiconductor charge material, and crystal growth proceeds by a liquid encapsulated, vertical gradient freeze process. About half of the crystals grown have a dislocation density of less than 1000/cm.sup.2. If the oxide of boron has water content less than 600 ppm, the crucible material should include boron nitride, a layer of the inner surface of the crucible should be oxidized before the oxide of boron in the crucible charge is melted, and the sum of thicknesses of the solid boron oxide layer and liquid boron oxide layer should be at least 50 .mu.m.

  11. Hydrogen Bonding: Between Strengthening the Crystal Packing and Improving Solubility of Three Haloperidol Derivatives

    Directory of Open Access Journals (Sweden)

    Hardeep Saluja

    2016-06-01

    Full Text Available The purpose of this study is to confirm the impact of polar functional groups on inter and intra-molecular hydrogen bonding in haloperidol (HP and droperidol (DP and, hence, their effects on dissolution using a new approach. To confirm our theory, a new molecule: deshydroxy-haloperidol (DHP was designed and its synthesis was requested from a contract laboratory. The molecule was then studied and compared to DP and HP. Unlike DHP, both the HP and DP molecules have hydrogen donor groups, therefore, DHP was used to confirm the relative effects of the hydrogen donor group on solubility and crystal packing. The solid dispersions of the three structurally related molecules: HP, DP, and DHP were prepared using PVPK30, and characterized using XRPD and IR. A comparative dissolution study was carried out in aqueous medium. The absence of a hydrogen bonding donor group in DHP resulted in an unexpected increase in its aqueous solubility and dissolution rate from solid dispersion, which is attributed to weaker crystal pack. The increased dissolution rate of HP and DP from solid dispersions is attributed to drug-polymer hydrogen bonding that interferes with the drug-drug intermolecular hydrogen bonding and provides thermodynamic stability of the dispersed drug molecules. The drug-drug intermolecular hydrogen bond is the driving force for precipitation and crystal packing.

  12. Studies on the relation between the size and dispersion of metallic silver nanoparticles and morphologies of initial silver(I) coordination polymer precursor

    Science.gov (United States)

    Moradi, Zhaleh; Akhbari, Kamran; Phuruangrat, Anukorn; Costantino, Ferdinando

    2017-04-01

    Micro and nano-structures of [Ag2(μ2-dcpa)2]n (1), [Hdcpa = 2,4-dichlorophenoxyacetic acid] which is a one-dimensional coordination polymer with corrugated tape chains, were synthesized as the bulk sample (1B), by sonochemical process (1S) and from mechanochemical reaction (1M). These three samples have been used as new precursors for fabricating silver nanoparticles via direct calcination at 300 °C and also thermal decomposition in oleic acid (OA) as a surfactant at 180 °C. In the presence of OA less agglomerated nanostructures were formed. It seems that the size, dispersion, morphology and agglomeration of initial precursor have direct influence on size, dispersion, morphology and agglomeration of metallic silver. This coordination polymer with various micro and nano morphologies were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Thermal stability of these samples were studied and compared with each other, too.

  13. Relating hydrogen-bonding interactions with the phase behavior of naproxen/PVP K 25 solid dispersions: evaluation of solution-cast and quench-cooled films.

    Science.gov (United States)

    Paudel, Amrit; Nies, Erik; Van den Mooter, Guy

    2012-11-05

    In this work, we investigated the relationship between various intermolecular hydrogen-bonding (H-bonding) interactions and the miscibility of the model hydrophobic drug naproxen with the hydrophilic polymer polyvinylpyrrolidone (PVP) across an entire composition range of solid dispersions prepared by quasi-equilibrium film casting and nonequilibrium melt quench cooling. The binary phase behavior in solid dispersions exhibited substantial processing method dependence. The solid state solubility of crystalline naproxen in PVP to form amorphous solid dispersions was 35% and 70% w/w naproxen in solution-cast films and quench-cooled films, respectively. However, the presence of a single mixed phase glass transition indicated the amorphous miscibility to be 20% w/w naproxen for the films, beyond which amorphous-amorphous and/or crystalline phase separations were apparent. This was further supported by the solution state interactions data such as PVP globular size distribution and solution infrared spectral profiles. The borderline melt composition showed cooling rate dependence of amorphization. The glass transition and melting point depression profiles of the system were treated with the analytical expressions based on Flory-Huggins mixing theory to interpolate the equilibrium solid solubility. FTIR analysis and subsequent spectral deconvolution revealed composition and miscibility dependent variations in the strength of drug-polymer intermolecular H-bonding. Two types of H-bonded populations were evidenced from 25% w/w and 35% w/w naproxen in solution-cast films and quench-cooled films, respectively, with the higher fraction of strongly H-bonded population in the drug rich domains of phase separated amorphous film compositions and highly drug loaded amorphous quench-cooled dispersions.

  14. Theoretical Analysis of the Relative Significance of Thermodynamic and Kinetic Dispersion in the dc and ac Voltammetry of Surface-Confined Molecules

    KAUST Repository

    Morris, Graham P.

    2015-05-05

    © 2015 American Chemical Society. Commonly, significant discrepancies are reported in theoretical and experimental comparisons of dc voltammograms derived from a monolayer or close to monolayer coverage of redox-active surface-confined molecules. For example, broader-than-predicted voltammetric wave shapes are attributed to the thermodynamic or kinetic dispersion derived from distributions in reversible potentials (E0) and electrode kinetics (k0), respectively. The recent availability of experimentally estimated distributions of E0 and k0 values derived from the analysis of data for small numbers of surface-confined modified azurin metalloprotein molecules now allows more realistic modeling to be undertaken, assuming the same distributions apply under conditions of high surface coverage relevant to voltammetric experiments. In this work, modeling based on conventional and stochastic kinetic theory is considered, and the computationally far more efficient conventional model is shown to be equivalent to the stochastic one when large numbers of molecules are present. Perhaps unexpectedly, when experimentally determined distributions of E0 and k0 are input into the model, thermodynamic dispersion is found to be unimportant and only kinetic dispersion contributes significantly to the broadening of dc voltammograms. Simulations of ac voltammetric experiments lead to the conclusion that the ac method, particularly when the analysis of kinetically very sensitive higher-order harmonics is undertaken, are far more sensitive to kinetic dispersion than the dc method. ac methods are therefore concluded to provide a potentially superior strategy for addressing the inverse problem of determining the k0 distribution that could give rise to the apparent anomalies in surface-confined voltammetry.

  15. The dispersion of radon in the Straz-Hamr area of the Czech Republic as an effect of uranium mining and related activities

    International Nuclear Information System (INIS)

    Smetana, R.; Novak, J.

    1997-01-01

    Uranium is exploited in the deposit Straz pod Ralskem-Hamr since 1968. During all the time two mining methods have existed side by side - the deep mining and the ''in situ leaching'' technology using the sulphuric acid. The uranium mining culminated in the second half of 1980s in the deposit. Higher concentrations of radon is expected in the uranium mining area. It is caused for one thing by higher content of the mother elements in the crust of the earth, for another by the various mining and reprocessing processes. To evaluate a radon exposure in the Straz-Hamr area an analysis of radon distribution was worked out. The analysis was prepared in 1986 in the mining company Uranove doly Hamr (now DIAMO s.p.) and it described dispersion of radon emitted to the air in connection with the mining activities. The sources of radon could be divided into two groups - area sources (leaching fields, ore depots, water basins) and point sources (stacks, ventilation boreholes, ventilators). This paper describes the methodology of the radon dispersion calculation, based on the stationary Gaussian model of dispersion of the gaseous contaminants from the point source. Modification of the methodology for the area sources and extension for the radioactive decay are also presented. Results of the calculations are represented graphically in the contour maps of the ground-level concentrations of radon and an assessment of the doses for the critical group is presented. (author)

  16. Synthesis, crystal structure, and properties of a perovskite-related bismuth phase, (NH43Bi2I9

    Directory of Open Access Journals (Sweden)

    Shijing Sun

    2016-03-01

    Full Text Available Organic-inorganic halide perovskites, especially methylammonium lead halide, have recently led to remarkable advances in photovoltaic devices. However, due to environmental and stability concerns around the use of lead, research into lead-free perovskite structures has been attracting increasing attention. In this study, a layered perovskite-like architecture, (NH43Bi2I9, is prepared from solution and the structure solved by single crystal X-ray diffraction. The band gap, which is estimated to be 2.04 eV using UV-visible spectroscopy, is lower than that of CH3NH3PbBr3. The energy-minimized structure obtained from first principles calculations is in excellent agreement with the X-ray results and establishes the locations of the hydrogen atoms. The calculations also point to a significant lone pair effect on the bismuth ion. Single crystal and powder conductivity measurements are performed to examine the potential application of (NH43Bi2I9 as an alternative to the lead containing perovskites.

  17. Synthesis, crystal structure, and properties of a perovskite-related bismuth phase, (NH4)3Bi2I9

    Science.gov (United States)

    Sun, Shijing; Tominaka, Satoshi; Lee, Jung-Hoon; Xie, Fei; Bristowe, Paul D.; Cheetham, Anthony K.

    2016-03-01

    Organic-inorganic halide perovskites, especially methylammonium lead halide, have recently led to remarkable advances in photovoltaic devices. However, due to environmental and stability concerns around the use of lead, research into lead-free perovskite structures has been attracting increasing attention. In this study, a layered perovskite-like architecture, (NH4)3Bi2I9, is prepared from solution and the structure solved by single crystal X-ray diffraction. The band gap, which is estimated to be 2.04 eV using UV-visible spectroscopy, is lower than that of CH3NH3PbBr3. The energy-minimized structure obtained from first principles calculations is in excellent agreement with the X-ray results and establishes the locations of the hydrogen atoms. The calculations also point to a significant lone pair effect on the bismuth ion. Single crystal and powder conductivity measurements are performed to examine the potential application of (NH4)3Bi2I9 as an alternative to the lead containing perovskites.

  18. Studying the Impact of Modified Saccharides on the Molecular Dynamics and Crystallization Tendencies of Model API Nifedipine.

    Science.gov (United States)

    Kaminska, E; Tarnacka, M; Wlodarczyk, P; Jurkiewicz, K; Kolodziejczyk, K; Dulski, M; Haznar-Garbacz, D; Hawelek, L; Kaminski, K; Wlodarczyk, A; Paluch, M

    2015-08-03

    Molecular dynamics of pure nifedipine and its solid dispersions with modified carbohydrates as well as the crystallization kinetics of active pharmaceutical ingredient (API) above and below the glass transition temperature were studied in detail by means of broadband dielectric spectroscopy (BDS), differential scanning calorimetry (DSC), and X-ray diffraction method. It was found that the activation barrier of crystallization increases in molecular dispersions composed of acetylated disaccharides, whereas it slightly decreases in those consisting of modified monocarbohydrates for the experiments carried out above the glass transition temperature. As shown by molecular dynamics simulations it can be related to the strength, character, and structure of intermolecular interactions between API and saccharides, which vary dependently on the excipient. Long-term physical stability studies showed that, in solid dispersions consisting of acetylated maltose and acetylated sucrose, the crystallization of nifedipine is dramatically slowed down, although it is still observable for a low concentration of excipients. With increasing content of modified carbohydrates, the crystallization of API becomes completely suppressed. This is most likely due to additional barriers relating to the intermolecular interactions and diffusion of nifedipine that must be overcome to trigger the crystallization process.

  19. Dispersion and current measurements

    International Nuclear Information System (INIS)

    Boelskifte, S.

    1986-04-01

    A model for the simulation of particle movements in water should incorporate the mutual distance dependent correlation. As long as reliable data are given accessible a model can be created of the dispersion in a given area from a statistical description of turbulence. Current measurements have been performed in an area north of the Swedish nuclear power plant Barsebaeck, and statistical time series analysis have made it possible to estimate multivariate autoregressive moving-average (ARMA) models for these data using the Box-Jenkins method. The correlation structure for the area has been investigated in detail. Transport and dispersion models for the marine environment are used in estimating doses to the population from the aquatic food chain. Some of these models are described with special emphasis on the time and length scales they cover. Furthermore, to illustrate the background of the simulation model, short introductuions are given to health physics, time series analysis, and turbulence theory. Analysis of the simulation model shows the relative importance of the different parameters. The model can be expanded to conditional simulation, where the current measurements are used directly to simulate the movement of one of the particles. Results from the model are also compared to results from a sampling of bioindicators (Fucus vesiculosus) along the Danish coast. The reliability of bioindicators in this kind of experiment is discussed. (author)

  20. Reflective Cholesteric Liquid Crystal Displays.

    Science.gov (United States)

    Lu, Zhijian

    Reflective cholesteric displays have two states at zero field, a Bragg reflecting planar texture and a weakly scattering focal conic texture. The performance of such a display depends on the stability and optical property of these textures. In this dissertation, various surface alignment layers are studied in order to optimize display performance and to understand physical and optical properties. Results show that non-homogeneous alignment layers fracture the planar texture and produce a multidomain structure as well as stabilize the focal conic texture. In the multidomain structure, the orientations of helical axes are distributed about the normal of the display cell, resulting in a wide viewing angle. The reflecting properties of the multidomain planar texture are quantitatively modeled using Berreman's 4 x 4 formalism. A gaussian type function adequately describe the helical axis orientation distribution. When the alignment condition is varied from tangential to homeotropic, the orientation of the helical axes becomes more broadly distributed. Reflective displays with high contrast ratios and wide viewing angles are achieved by using tilted or homeotropic alignment layers. The switching mechanism between the two stable textures of the reflective displays is of great importance not only for designing drive scheme but also for understanding the fundamental dynamics of the texture transitions. Planar texture can be transformed into focal conic texture directly by applying a relatively low field. The transition from focal conic to planar texture can only be realized by first switching the cholesteric liquid crystals into the homeotropic texture and then allowing the homeotropic texture to relax to the planar texture. In the relaxation, a transient planar texture with pitch, {K_{33 }over K_{22}}P_ {o} is observed by using optical reflection measurement. The transition time from the homeotropic texture to the transient planar texture is on the order of 1 ms and is

  1. Relating mechanical properties and chemical bonding in an inorganic-organic framework material: a single-crystal nanoindentation study.

    Science.gov (United States)

    Tan, Jin Chong; Furman, Joshua D; Cheetham, Anthony K

    2009-10-14

    We report the application of nanoindentation and atomic force microscopy to establish the fundamental relationships between mechanical properties and chemical bonding in a dense inorganic-organic framework material: Ce(C(2)O(4))(HCO(2)), 1. Compound 1 is a mixed-ligand 3-D hybrid which crystallizes in an orthorhombic space group, in which its three basic building blocks, i.e. the inorganic metal-oxygen-metal (M-O-M) chains and the two organic bridging ligands, (oxalate and formate) are all oriented perpendicular to one another. This unique architecture enabled us to decouple the elastic and plastic mechanical responses along the three primary axes of a single crystal to understand the contribution associated with stiff vs compliant basic building blocks. The (001)-oriented facet that features rigid oxalate ligands down the c-axis exhibits the highest stiffness and hardness (E approximately 78 GPa and H approximately 4.6 GPa). In contrast, the (010)-oriented facet was found to be the most compliant and soft (E approximately 43 GPa and H approximately 3.9 GPa), since the formate ligand, which is the more compliant building block within this framework, constitutes the primary linkages down the b-axis. Notably, intermediate stiffness and hardness (E approximately 52 GPa and H approximately 4.1 GPa) were measured on the (100)-oriented planes. This can be attributed to the Ce-O-Ce chains that zigzag down the a-axis (Ce...Ce metal centers form an angle of approximately 132 degrees) and also the fact that the 9-coordinated CeO(9) polyhedra are expected to be geometrically more compliant. Our results present the first conclusive evidence that the crystal orientation dominated by inorganic chains is not necessarily more robust from the mechanical properties standpoint. Rigid organic bridging ligands (such as oxalate), on the other hand, can be used to produce greater stiffness and hardness properties in a chosen crystallographic orientation. This study demonstrates that

  2. On Dispersion in Visual Photoreceptors

    NARCIS (Netherlands)

    Stavenga, D.G.; Barneveld, H.H. van

    1975-01-01

    An idealized visual pigment absorbance spectrum is used together with a Kramers-Kronig dispersion relation to calculate the contribution of the visual pigment to the refractive index of the fly photoreceptor. It appears that an absorption coefficient of 0.010 µm-1 results in a refractive index

  3. Crystal growth and crystallography

    Science.gov (United States)

    Chernov, A. A.

    1998-01-01

    Selected topics that may be of interest for both crystal-structure and crystal-growth communities are overviewed. The growth of protein crystals, along with that of some other compounds, is one of the topics, and recent insights into related phenomena are considered as examples of applications of general principles. The relationship between crystal growth shape and structure is reviewed and an attempt to introduce semiquantitative characterization of binding for proteins is made. The concept of kinks for complex structures is briefly discussed. Even at sufficiently low supersaturations, the fluctuation of steps may not be sufficient to implement the Gibbs-Thomson law if the kink density is low enough. Subsurface ordering of liquids and growth of rough interfaces from melts is discussed. Crystals growing in microgravity from solution should be more perfect if they preferentially trap stress-inducing impurities, thus creating an impurity-depleted zone around themselves. Evidently, such a zone is developed only around the crystals growing in the absence of convection. Under terrestrial conditions, the self-purified depleted zone is destroyed by convection, the crystal traps more impurity and grows stressed. The stress relief causes mosaicity. In systems containing stress-inducing but poorly trapped impurities, the crystals grown in the absence of convection should be worse than those of their terrestrial counterparts.

  4. Growth of single crystals of BaFe12O19 by solid state crystal growth

    International Nuclear Information System (INIS)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-01-01

    Single crystals of BaFe 12 O 19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe 12 O 19 are buried in BaFe 12 O 19 +1 wt% BaCO 3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe 12 O 19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe 12 O 19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth. - Highlights: • Single crystals of BaFe 12 O 19 are grown by solid state crystal growth. • A single crystal up to ∼130 μm thick (c-axis direction) grows on the seed crystal. • The single crystal and surrounding ceramic matrix have similar composition. • Micro-Raman scattering shows the single crystal has the BaFe 12 O 19 structure.

  5. Interfacial wave theory for dendritic structure of a growing needle crystal. I - Local instability mechanism. II - Wave-emission mechanism at the turning point

    Science.gov (United States)

    Xu, Jian-Jun

    1989-01-01

    The complicated dendritic structure of a growing needle crystal is studied on the basis of global interfacial wave theory. The local dispersion relation for normal modes is derived in a paraboloidal coordinate system using the multiple-variable-expansion method. It is shown that the global solution in a dendrite growth process incorporates the morphological instability factor and the traveling wave factor.

  6. Impact of communities, health, and emotional-related factors on smoking use: comparison of joint modeling of mean and dispersion and Bayes' hierarchical models on add health survey.

    Science.gov (United States)

    Pu, Jie; Fang, Di; Wilson, Jeffrey R

    2017-02-03

    The analysis of correlated binary data is commonly addressed through the use of conditional models with random effects included in the systematic component as opposed to generalized estimating equations (GEE) models that addressed the random component. Since the joint distribution of the observations is usually unknown, the conditional distribution is a natural approach. Our objective was to compare the fit of different binary models for correlated data in Tabaco use. We advocate that the joint modeling of the mean and dispersion may be at times just as adequate. We assessed the ability of these models to account for the intraclass correlation. In so doing, we concentrated on fitting logistic regression models to address smoking behaviors. Frequentist and Bayes' hierarchical models were used to predict conditional probabilities, and the joint modeling (GLM and GAM) models were used to predict marginal probabilities. These models were fitted to National Longitudinal Study of Adolescent to Adult Health (Add Health) data for Tabaco use. We found that people were less likely to smoke if they had higher income, high school or higher education and religious. Individuals were more likely to smoke if they had abused drug or alcohol, spent more time on TV and video games, and been arrested. Moreover, individuals who drank alcohol early in life were more likely to be a regular smoker. Children who experienced mistreatment from their parents were more likely to use Tabaco regularly. The joint modeling of the mean and dispersion models offered a flexible and meaningful method of addressing the intraclass correlation. They do not require one to identify random effects nor distinguish from one level of the hierarchy to the other. Moreover, once one can identify the significant random effects, one can obtain similar results to the random coefficient models. We found that the set of marginal models accounting for extravariation through the additional dispersion submodel produced

  7. Development of certain aspects of colloid chemistry and physical-chemical mechanics of disperse systems and materials in relation to stability of slopes and grades

    Directory of Open Access Journals (Sweden)

    A.N. Plugin

    2011-12-01

    Full Text Available In the article the motive force of the movement the particles in dispersed systems, which include soils, when load is just sole weight of the array was investigated. It is shown that the shearing force of the weight of the soil and the specific cohesion which taken into account in calculating the stability of slopes of embankments and landslides on the slopes, much less than real. The calculations showed that the electrophoretic mechanism is a very real explanation of the observed sliding the upper part of the slope.

  8. Equatorward dispersion of a high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009

    Science.gov (United States)

    Wu, Xue; Griessbach, Sabine; Hoffmann, Lars

    2017-11-01

    Tropical volcanic eruptions have been widely studied for their significant contribution to stratospheric aerosol loading and global climate impacts, but the impact of high-latitude volcanic eruptions on the stratospheric aerosol layer is not clear and the pathway of transporting aerosol from high latitudes to the tropical stratosphere is not well understood. In this work, we focus on the high-latitude volcano Sarychev (48.1° N, 153.2° E), which erupted in June 2009, and the influence of the Asian summer monsoon (ASM) on the equatorward dispersion of the volcanic plume. First, the sulfur dioxide (SO2) emission time series and plume height of the Sarychev eruption are estimated with SO2 observations of the Atmospheric Infrared Sounder (AIRS) and a backward trajectory approach using the Lagrangian particle dispersion model Massive-Parallel Trajectory Calculations (MPTRAC). Then, the transport and dispersion of the plume are simulated using the derived SO2 emission time series. The transport simulations are compared with SO2 observations from AIRS and validated with aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The MPTRAC simulations show that about 4 % of the sulfur emissions were transported to the tropical stratosphere within 50 days after the beginning of the eruption, and the plume dispersed towards the tropical tropopause layer (TTL) through isentropic transport above the subtropical jet. The MPTRAC simulations and MIPAS aerosol data both show that between the potential temperature levels of 360 and 400 K, the equatorward transport was primarily driven by anticyclonic Rossby wave breaking enhanced by the ASM in boreal summer. The volcanic plume was entrained along the anticyclone flows and reached the TTL as it was transported southwestwards into the deep tropics downstream of the anticyclone. Further, the ASM anticyclone influenced the pathway of aerosols by isolating an aerosol hole inside of the ASM, which

  9. RNA Crystallization

    Science.gov (United States)

    Golden, Barbara L.; Kundrot, Craig E.

    2003-01-01

    RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

  10. Liquid crystals in tribology.

    Science.gov (United States)

    Carrión, Francisco-José; Martínez-Nicolás, Ginés; Iglesias, Patricia; Sanes, José; Bermúdez, María-Dolores

    2009-09-18

    Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered.

  11. Effect of boron carbide on primary crystallization of chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2008-04-01

    Full Text Available In the paper results of the influence of boron carbide (B4C as inoculant of abrasion-resisting chromium cast iron (about 2,8% carbon and 18% chromium on primary crystallization researches are presented. Boron carbide dispersion was introduced at the bottom of pouring ladle before tap of liquid cast iron. In this investigations were used three different quantities of inoculant in amounts 0,1%; 0,2% and 0,3% with relation to bath weight. It has been demonstrated that such small additions of boron carbide change primary crystallization parameters, particularly temperature characteristic of process, their time and kinetics.

  12. Resonant Goos-Hänchen and Imbert-Fedorov shifts at photonic crystal slabs

    Science.gov (United States)

    Paul, Thomas; Rockstuhl, Carsten; Menzel, Christoph; Lederer, Falk

    2008-05-01

    We show that a longitudinal (Goos-Hänchen) and a transverse (Imbert-Fedorov) beam displacement can be observed upon total internal reflection at two-dimensional photonic crystal slabs. By inspecting only the dispersion relation of the photonic crystal we derive qualitative criteria for the direction of the beam shift. Furthermore, it will be shown that the beam shift can be strongly enhanced at particular angles of incidence where Fabry-Pérot resonances of the slab are excited. The Renard model, which predicts the strength of the shifts based on the Poynting vector in the totally reflecting medium, has been adapted to quantitatively analyze the beam shift.

  13. GROWTH RATE DISTRIBUTION OF BORAX SINGLE CRYSTALS ON THE (001 FACE UNDER VARIOUS FLOW RATES

    Directory of Open Access Journals (Sweden)

    Suharso Suharso

    2010-06-01

    Full Text Available The growth rates of borax single crystals from aqueous solutions at various flow rates in the (001 direction were measured using in situ cell method. From the growth rate data obtained, the growth rate distribution of borax crystals was investigated using Minitab Software and SPSS Software at relative supersaturation of 0807 and temperature of 25 °C. The result shows that normal, gamma, and log-normal distribution give a reasonably good fit to GRD. However, there is no correlation between growth rate distribution and flow rate of solution.   Keywords: growth rate dispersion (GRD, borax, flow rate

  14. Frequency Doubling Broadband Light in Multiple Crystals

    International Nuclear Information System (INIS)

    Alford, William J.; Smith, Arlee V.

    2000-01-01

    The authors compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk off compensation, and with doubling in five crystals adjusted for offset phase matching frequencies. Using a plane-wave, dispersive numerical model of frequency doubling they study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance the offset phase matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second harmonic bandwidth. The walk off compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single crystal efficiency while maintaining broad bandwidth

  15. Preparation and Characterization of Polypropylene / MWCNT Dispersions

    Science.gov (United States)

    Pujari, Saswati; Burghardt, Wesley; Ramanathan, Thillaiyan; Brinson, L. Catherine; Kasimatis, Kosmas; Torkelson, John

    2008-03-01

    Dispersions of multiwall carbon nanotubes in polypropylene are prepared via melt batch mixing and solid-state shear pulverization, and characterized via linear viscoelastic measurements, SEM, polypropylene crystallization kinetics, electrical conductivity and dynamic mechanical analysis. Increasing the intensity or duration of the melt mixing leads to higher dispersion, evidenced by increases in a low-frequency elastic plateau and accelerated PP crystallization kinetics attributed to more effective heterogeneous nucleation. The sample prepared by pulverization exhibits faster crystallization kinetics than any of the melt blended samples, but in contrast shows no measurable low frequency elastic plateau. Electrical conductivity measurements similarly show higher conductivity in melt blended samples. This may be attributable to scission of the nanotubes during pulverization, such that even well dispersed tubes cannot form an entangled network at a given concentration. At the same time, pulverized composites show marked increase in stiffness at low loadings, indicating that tube scission due to pulverization is not catastrophic. Conversely, long mixing times required in melt blending cause substantial thermal degradation of the polymer matrix with a corresponding loss of mechanical properties.

  16. Application of Thin Films of Conjugated Polymers in Novel LED's and Liquid Crystal 'Light Valves'

    National Research Council Canada - National Science Library

    MacDiarmid, A

    1997-01-01

    .... Flexible, completely organic polymer dispersed liquid crystal light valves have been fabricated from transparent plastic substrates on which a conducting film of polypyrrole has been deposited...

  17. Dispersion-induced nonlinearities in semiconductors

    DEFF Research Database (Denmark)

    Mørk, Jesper; Mecozzi, A.

    2002-01-01

    A dispersive and saturable medium is shown, under very general conditions, to possess ultrafast dynamic behaviour due to non-adiabatic polarisation dynamics. Simple analytical expressions relating the effect to the refractive index dispersion of a semiconductor ire derived and the magnitude...... of the equivalent Kerr coefficient is shown to be in qualitative agreement with measurements on active semiconductor waveguides....

  18. Dispersion management with metamaterials

    Science.gov (United States)

    Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2017-03-07

    An apparatus, system, and method to counteract group velocity dispersion in fibers, or any other propagation of electromagnetic signals at any wavelength (microwave, terahertz, optical, etc.) in any other medium. A dispersion compensation step or device based on dispersion-engineered metamaterials is included and avoids the need of a long section of specialty fiber or the need for Bragg gratings (which have insertion loss).

  19. Impact of communities, health, and emotional-related factors on smoking use: comparison of joint modeling of mean and dispersion and Bayes’ hierarchical models on add health survey

    Directory of Open Access Journals (Sweden)

    Jie Pu

    2017-02-01

    Full Text Available Abstract Background The analysis of correlated binary data is commonly addressed through the use of conditional models with random effects included in the systematic component as opposed to generalized estimating equations (GEE models that addressed the random component. Since the joint distribution of the observations is usually unknown, the conditional distribution is a natural approach. Our objective was to compare the fit of different binary models for correlated data in Tabaco use. We advocate that the joint modeling of the mean and dispersion may be at times just as adequate. We assessed the ability of these models to account for the intraclass correlation. In so doing, we concentrated on fitting logistic regression models to address smoking behaviors. Methods Frequentist and Bayes’ hierarchical models were used to predict conditional probabilities, and the joint modeling (GLM and GAM models were used to predict marginal probabilities. These models were fitted to National Longitudinal Study of Adolescent to Adult Health (Add Health data for Tabaco use. Results We found that people were less likely to smoke if they had higher income, high school or higher education and religious. Individuals were more likely to smoke if they had abused drug or alcohol, spent more time on TV and video games, and been arrested. Moreover, individuals who drank alcohol early in life were more likely to be a regular smoker. Children who experienced mistreatment from their parents were more likely to use Tabaco regularly. Conclusions The joint modeling of the mean and dispersion models offered a flexible and meaningful method of addressing the intraclass correlation. They do not require one to identify random effects nor distinguish from one level of the hierarchy to the other. Moreover, once one can identify the significant random effects, one can obtain similar results to the random coefficient models. We found that the set of marginal models accounting for

  20. Hydrogen related crystallization in intrinsic hydrogenated amorphous silicon films prepared by reactive radiofrequency magnetron sputtering at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Senouci, D. [Laboratoire de Genie Physique, Universite Ibn-Khaldoun, 14000 Tiaret (Algeria); LPCMME, Departement de Physique, Universite d' Oran Es-senia, 3100, Oran (Algeria); Baghdad, R., E-mail: r_baghdad@mail.univ-tiaret.dz [Laboratoire de Genie Physique, Universite Ibn-Khaldoun, 14000 Tiaret (Algeria); Belfedal, A.; Chahed, L. [LPCMME, Departement de Physique, Universite d' Oran Es-senia, 3100, Oran (Algeria); Portier, X. [CIMAP, CEA, CNRS UMR 6252-ENSICAEN, UCBN, 6 Bvd Marechal Juin, 14050 Caen Cedex (France); Charvet, S. [LPMC, UFR des Sciences, Universite de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens (France); Kim, K.H. [LPICM, Laboratoire de Physique des Interfaces et Couches Minces, CNRS UMR 7647, Ecole Polytechnique, 91128 Palaiseau (France); TOTAL S.A., Gas and Power, R and D Division, Courbevoie (France); Roca i Cabarrocas, P. [LPICM, Laboratoire de Physique des Interfaces et Couches Minces, CNRS UMR 7647, Ecole Polytechnique, 91128 Palaiseau (France); Zellama, K. [LPMC, UFR des Sciences, Universite de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens (France)

    2012-11-01

    We present an investigation on the transition from amorphous to nanocrystalline silicon and associated hydrogen changes during the first steps of hydrogenated nanocrystalline silicon growth for films elaborated by reactive radiofrequency magnetron sputtering at a substrate temperature as low as room temperature and for deposition times varying from 3 to 60 min. Complementary experimental techniques have been used to characterize the films in their as-deposited state. They are completed by thermal hydrogen effusion experiments conducted in the temperature range, from room temperature to 800 Degree-Sign C. The results show that, during the initial stages of growth, the presence of a hydrogen-rich layer is necessary to initiate the crystallization process. - Highlights: Black-Right-Pointing-Pointer Nanocrystalline silicon growth at room temperature. Black-Right-Pointing-Pointer Transition from amorphous to nanocrystalline silicon. Black-Right-Pointing-Pointer Chemical reactions of H atoms with strained Si-Si bonds. Black-Right-Pointing-Pointer H selective etching and chemical transport caused the silicon nucleation.